docs(various): Improve readability. Signed-off-by: Ryan Russell <git@ryanrussell.org>

### Description
Improve readability

This patch simplifies the compilation process for the pysolvers extension.
As a result, all the solvers are compiled by em++, which makes lingeling
difficult to compile. Solving this issue seems possible eventually but it
requires more effort to put, which might be not worth it at this point.

diff --git a/setup.py b/setup.py
index 82dac9c..3fe102f 100644
--- a/setup.py
+++ b/setup.py
@@ -69,8 +69,8 @@ Details can be found at `https://pysathq.github.io <https://pysathq.github.io>`_
 # solvers to install
 #==============================================================================
 to_install = ['cadical', 'gluecard30', 'gluecard41', 'glucose30', 'glucose41',
-        'lingeling', 'maplechrono', 'maplecm', 'maplesat', 'mergesat3',
-        'minicard', 'minisat22', 'minisatgh']
+        'maplechrono', 'maplecm', 'maplesat', 'mergesat3', 'minicard',
+        'minisat22', 'minisatgh']
 
 # example scripts to install as standalone executables
 #==============================================================================
@@ -78,47 +78,9 @@ scripts = ['fm', 'genhard', 'lbx', 'lsu', 'mcsls', 'models', 'musx', 'optux',
         'rc2']
 
 
-# we need to redefine the build command to
-# be able to download and compile solvers
-#==============================================================================
-class build(distutils.command.build.build):
-    """
-        Our custom builder class.
-    """
-
-    def run(self):
-        """
-            Download, patch and compile SAT solvers before building.
-        """
-        # download and compile solvers
-        if platform.system() != 'Windows':
-            prepare.do(to_install)
-
-        # now, do standard build
-        distutils.command.build.build.run(self)
-
-# same with build_ext
-#==============================================================================
-class build_ext(distutils.command.build_ext.build_ext):
-    """
-        Our custom builder class.
-    """
-
-    def run(self):
-        """
-            Download, patch and compile SAT solvers before building.
-        """
-        # download and compile solvers
-        if platform.system() != 'Windows':
-            prepare.do(to_install)
-
-        # now, do standard build
-        distutils.command.build_ext.build_ext.run(self)
-
-
 # compilation flags for C extensions
 #==============================================================================
-compile_flags, cpplib = ['-std=c++11', '-Wall', '-Wno-deprecated'],  ['stdc++']
+compile_flags, cpplib = ['-std=c++11', '-O3', '-Wall', '-Wno-deprecated', '-DQUIET'],  ['stdc++']
 if platform.system() == 'Darwin':
     compile_flags += ['--stdlib=libc++']
     cpplib = ['c++']
@@ -141,23 +103,19 @@ pycard_ext = Extension('pycard',
 
 pysolvers_sources = ['solvers/pysolvers.cc']
 
-if platform.system() == 'Windows':
-    prepare.do(to_install)
-    with chdir('solvers'):
-        for solver in to_install:
-            with chdir(solver):
-                for filename in glob.glob('*.c*'):
-                    pysolvers_sources += ['solvers/%s/%s' % (solver, filename)]
-                for filename in glob.glob('*/*.c*'):
-                    pysolvers_sources += ['solvers/%s/%s' % (solver, filename)]
-    libraries = []
-    library_dirs = []
-else:
-    libraries = to_install + cpplib
-    library_dirs = list(map(lambda x: os.path.join('solvers', x), to_install))
+prepare.do(to_install)
+with chdir('solvers'):
+    for solver in to_install:
+        with chdir(solver):
+            for filename in glob.glob('*.c*'):
+                pysolvers_sources += ['solvers/%s/%s' % (solver, filename)]
+            for filename in glob.glob('*/*.c*'):
+                pysolvers_sources += ['solvers/%s/%s' % (solver, filename)]
+libraries = []
+library_dirs = []
 
 pysolvers_ext = Extension('pysolvers',
-    sources=pysolvers_sources,
+    sources=sorted(pysolvers_sources),
     extra_compile_args=compile_flags + \
         list(map(lambda x: '-DWITH_{0}'.format(x.upper()), to_install)),
     include_dirs=['solvers'],
@@ -182,7 +140,6 @@ setup(name='python-sat',
     url='https://github.com/pysathq/pysat',
     ext_modules=[pycard_ext, pysolvers_ext],
     scripts=['examples/{0}.py'.format(s) for s in scripts],
-    cmdclass={'build': build, 'build_ext': build_ext},
     install_requires=['six'],
     extras_require = {
         'aiger': ['py-aiger-cnf>=2.0.0'],
diff --git a/solvers/prepare.py b/solvers/prepare.py
index a1b5e91..464e1d1 100644
--- a/solvers/prepare.py
+++ b/solvers/prepare.py
@@ -520,8 +520,6 @@ def do(to_install):
         adapt_files(solver)
         patch_solver(solver)
 
-        if platform.system() != 'Windows':
-            compile_solver(solver)
 
 #
 #==============================================================================

This patch simplifies the compilation process for the pysolvers extension.
As a result, all the solvers are compiled by em++, which makes lingeling
difficult to compile. Solving this issue seems possible eventually but it
requires more effort to put, which might be not worth it at this point.

diff --git a/setup.py b/setup.py
index 82dac9c..3fe102f 100644
--- a/setup.py
+++ b/setup.py
@@ -69,8 +69,8 @@ Details can be found at `https://pysathq.github.io <https://pysathq.github.io>`_
 # solvers to install
 #==============================================================================
 to_install = ['cadical', 'gluecard30', 'gluecard41', 'glucose30', 'glucose41',
-        'lingeling', 'maplechrono', 'maplecm', 'maplesat', 'mergesat3',
-        'minicard', 'minisat22', 'minisatgh']
+        'maplechrono', 'maplecm', 'maplesat', 'mergesat3', 'minicard',
+        'minisat22', 'minisatgh']
 
 # example scripts to install as standalone executables
 #==============================================================================
@@ -78,47 +78,9 @@ scripts = ['fm', 'genhard', 'lbx', 'lsu', 'mcsls', 'models', 'musx', 'optux',
         'rc2']
 
 
-# we need to redefine the build command to
-# be able to download and compile solvers
-#==============================================================================
-class build(distutils.command.build.build):
-    """
-        Our custom builder class.
-    """
-
-    def run(self):
-        """
-            Download, patch and compile SAT solvers before building.
-        """
-        # download and compile solvers
-        if platform.system() != 'Windows':
-            prepare.do(to_install)
-
-        # now, do standard build
-        distutils.command.build.build.run(self)
-
-# same with build_ext
-#==============================================================================
-class build_ext(distutils.command.build_ext.build_ext):
-    """
-        Our custom builder class.
-    """
-
-    def run(self):
-        """
-            Download, patch and compile SAT solvers before building.
-        """
-        # download and compile solvers
-        if platform.system() != 'Windows':
-            prepare.do(to_install)
-
-        # now, do standard build
-        distutils.command.build_ext.build_ext.run(self)
-
-
 # compilation flags for C extensions
 #==============================================================================
-compile_flags, cpplib = ['-std=c++11', '-Wall', '-Wno-deprecated'],  ['stdc++']
+compile_flags, cpplib = ['-std=c++11', '-O3', '-Wall', '-Wno-deprecated', '-DQUIET'],  ['stdc++']
 if platform.system() == 'Darwin':
     compile_flags += ['--stdlib=libc++']
     cpplib = ['c++']
@@ -141,23 +103,19 @@ pycard_ext = Extension('pycard',
 
 pysolvers_sources = ['solvers/pysolvers.cc']
 
-if platform.system() == 'Windows':
-    prepare.do(to_install)
-    with chdir('solvers'):
-        for solver in to_install:
-            with chdir(solver):
-                for filename in glob.glob('*.c*'):
-                    pysolvers_sources += ['solvers/%s/%s' % (solver, filename)]
-                for filename in glob.glob('*/*.c*'):
-                    pysolvers_sources += ['solvers/%s/%s' % (solver, filename)]
-    libraries = []
-    library_dirs = []
-else:
-    libraries = to_install + cpplib
-    library_dirs = list(map(lambda x: os.path.join('solvers', x), to_install))
+prepare.do(to_install)
+with chdir('solvers'):
+    for solver in to_install:
+        with chdir(solver):
+            for filename in glob.glob('*.c*'):
+                pysolvers_sources += ['solvers/%s/%s' % (solver, filename)]
+            for filename in glob.glob('*/*.c*'):
+                pysolvers_sources += ['solvers/%s/%s' % (solver, filename)]
+libraries = []
+library_dirs = []
 
 pysolvers_ext = Extension('pysolvers',
-    sources=pysolvers_sources,
+    sources=sorted(pysolvers_sources),
     extra_compile_args=compile_flags + \
         list(map(lambda x: '-DWITH_{0}'.format(x.upper()), to_install)),
     include_dirs=['solvers'],
@@ -182,7 +140,6 @@ setup(name='python-sat',
     url='https://github.com/pysathq/pysat',
     ext_modules=[pycard_ext, pysolvers_ext],
     scripts=['examples/{0}.py'.format(s) for s in scripts],
-    cmdclass={'build': build, 'build_ext': build_ext},
     install_requires=['six'],
     extras_require = {
         'aiger': ['py-aiger-cnf>=2.0.0'],
diff --git a/solvers/prepare.py b/solvers/prepare.py
index a1b5e91..464e1d1 100644
--- a/solvers/prepare.py
+++ b/solvers/prepare.py
@@ -520,8 +520,6 @@ def do(to_install):
         adapt_files(solver)
         patch_solver(solver)
 
-        if platform.system() != 'Windows':
-            compile_solver(solver)
 
 #
 #==============================================================================
