get_config_h_filename():  Support NT as well as Posix systems.
get_config_h_filename():  Support NT as well as Posix systems.

_init_nt():  Use get_config_h_filename() instead of figuring out the
             name directly.

             g['SO'] should be set to '.pyd'.

             Adjust some minor coding nits.

pypa/setuptools,pypa/setuptools,pypa/setuptools