setup.py: Provide a os.path.samefile fallback for Python 2 under Windows
setup.py: Provide a os.path.samefile fallback for Python 2 under Windows

os.path.samefile is missing from Python 2 under Windows. Implement a
simple fallback which normalizes and compares paths instead.

pexip/pygobject,GNOME/pygobject,pexip/pygobject,GNOME/pygobject,GNOME/pygobject,pexip/pygobject