rem: group_in_compile_stack (compile_stack, regnum) compile_stack_type compile_stack; regnum_t regnum;
add: group_in_compile_stack (compile_stack_type compile_stack, regnum_t regnum)
context: group_in_compile_stack (compile_stack, regnum)    compile_stack_type compile_stack;    regnum_t regnum;{  int this_element;  for (this_element = compile_stack.avail - 1;       this_element >= 0;       this_element--)    if (compile_stack.stack[this_element].regnum == regnum)      return true;  return false;}