Packages the distutils stdlib module as a standalone package,
```
377K distutils.data
221K distutils.data.br
19K distutils.js
```
to reduce the minimal pyodide size.

Part of #1542 

This also,
 - adds documentation on what's supported or not in the stdlib
 - makes a few changes to `pyodide_build/buildall.py` to be able to add such stdlib packages as a dependency in other packages (which didn't work before). For instance, until there is a release with https://github.com/pypa/packaging/pull/396 micropip has a dependency on distutils.
Unvendor distutils. Packages the distutils stdlib module as a standalone package,
```
377K distutils.data
221K distutils.data.br
19K distutils.js
```
to reduce the minimal pyodide size.

Part of #1542 

This also,
 - adds documentation on what's supported or not in the stdlib
 - makes a few changes to `pyodide_build/buildall.py` to be able to add such stdlib packages as a dependency in other packages (which didn't work before). For instance, until there is a release with https://github.com/pypa/packaging/pull/396 micropip has a dependency on distutils.
commit d6740caa7400105a578ace74f8c25bbb3434178c
Author: Roman Yurchak <rth.yurchak@pm.me>
Date:   Wed Oct 10 14:47:12 2018 +0200

    Disable scipy.stats.mvn

diff --git a/scipy/stats/kde.py b/scipy/stats/kde.py
index 7c702a038..8b0ab0254 100644
--- a/scipy/stats/kde.py
+++ b/scipy/stats/kde.py
@@ -32,7 +32,10 @@ import numpy as np
 from numpy.random import randint, multivariate_normal
 
 # Local imports.
-from . import mvn
+try:
+    from . import mvn
+except ImportError:
+    mvn = None
 
 
 __all__ = ['gaussian_kde']
diff --git a/scipy/stats/setup.py b/scipy/stats/setup.py
index f1a02df4e..7366ec12d 100755
--- a/scipy/stats/setup.py
+++ b/scipy/stats/setup.py
@@ -32,9 +32,9 @@ def configuration(parent_package='',top_path=None):
     )
 
     # add mvn module
-    config.add_extension('mvn',
-        sources=['mvn.pyf','mvndst.f'],
-    )
+    #config.add_extension('mvn',
+    #    sources=['mvn.pyf','mvndst.f'],
+    #)
 
     return config
 

commit d6740caa7400105a578ace74f8c25bbb3434178c
Author: Roman Yurchak <rth.yurchak@pm.me>
Date:   Wed Oct 10 14:47:12 2018 +0200

    Disable scipy.stats.mvn

diff --git a/scipy/stats/kde.py b/scipy/stats/kde.py
index 7c702a038..8b0ab0254 100644
--- a/scipy/stats/kde.py
+++ b/scipy/stats/kde.py
@@ -32,7 +32,10 @@ import numpy as np
 from numpy.random import randint, multivariate_normal
 
 # Local imports.
-from . import mvn
+try:
+    from . import mvn
+except ImportError:
+    mvn = None
 
 
 __all__ = ['gaussian_kde']
diff --git a/scipy/stats/setup.py b/scipy/stats/setup.py
index f1a02df4e..7366ec12d 100755
--- a/scipy/stats/setup.py
+++ b/scipy/stats/setup.py
@@ -32,9 +32,9 @@ def configuration(parent_package='',top_path=None):
     )
 
     # add mvn module
-    config.add_extension('mvn',
-        sources=['mvn.pyf','mvndst.f'],
-    )
+    #config.add_extension('mvn',
+    #    sources=['mvn.pyf','mvndst.f'],
+    #)
 
     return config
 
