Issue #593 and other fixes

- Fix issue #593
- Fix some forgotten "vcver" => "vc_ver" renames in previous commit.
- Add comment on why I didn't followed PEP8 for some variables names.

Remove extra redundant work. Patch the module so behavior is the same on Unix systems even if not invoked. Tests still pass on Linux due to import protections.

Update msvc9_support.py

Get real `site-packages`

build_ext: always import _CONFIG_VARS from distutils.sysconfig instead of sysconfig

Feature/msvc-discovery

README and CHANGES were renamed. Update MANIFEST.in to include them once again in the source distributions. Fixes #575.

otherwise `distutils.sysconfig.customize_compiler` does not configure OSX compiler for -dynamiclib

See https://github.com/pypa/setuptools/issues/571

After testing VC Builds Tools 2015 with current = Amd64 and target = Amd64, x86, Arm