Added "cp35" (and later "cp36", etc.) to the tag, so now it looks similar to PEP 425 without the ABI tag (ironically, since there's fundamentally no difference between the Python version and the ABI). "cp3" is also accepted for stable ABI extensions that still need a platform specifier.

distutils will always build extensions with the most specific tag, which I believe is best. If you want a different tag, then you currently need to do the build manually (unless there's a way to override the suffix distutils/setuptools uses? It didn't look like an obvious option)

I also added the tag into the stdlib pyds. This is kind of nice, but not really necessary. We don't (and probably can't) tag python.exe and python35.dll, so there's no opportunity to install different version/platform interpreters in the same directory anyway. It's a trivial change to remove, though it does further help test the mechanism (along with an importlib test to validate the tag value).

Example names with tags:

spam.cp35-win_amd64.pyd
spam_d.cp35-win32.pyd
spam.cp3-win32.pyd