Hello,

I modified "msvc9compiler.py" with following changes : 

- Add automatic compatibility with standalone VC++ compilers from Windows SDK 7.1. (Not for 6.1/7.0, because that finally don't work as good as it seem on first view and there is already MSVC++ for Python 2.7).
- Changed error when "include", "lib", "libpath" or "path" environment variable is missing to be more clear.
- Modified some comments and strings to not specify exclusively VS2008 (This file is also compatible with more recent VS and that was not really clear before)
- Remove "gen_preprocess_options" from import because it was unused.
- Fixed PEP8.

The file was tested with SDK7.1 on a Cython compilation + a Pip install from source on Python 3.4 and seem to work perfectly.

Ps: Forget my previous comment on VS2015, I didn't see that code for it was moved on "_msvccompiler.py". I'll wait the official release for the fix on Visual C++ Build Tools 2015 (Which is, anyway, only in technical preview since october)