remove explicit dependency on pywin32

Turns out we can hardcode 0x00000008 as per Microsoft docs:

http://msdn.microsoft.com/en-us/library/windows/desktop/ms684863(v=vs.85).aspx

You apparently can't install pywin32 via pip so this relieves a huge headache for us on MCI when we were trying to jam MO into a virtual env without getting it polluted with system site packages. Already in production on C++ driver Windows tests.