Patch to compile Polycode in VS2012 for Win64

- Change in PolyWinCore.cpp from SetClassLong to SetClassLongPtr for Win32
  and Win64 compatibility. See (1) and (2) for official Microsoft documentation on 
  SetClassLong and SetClassLongPtr, respectively.

(1) http://msdn.microsoft.com/en-us/library/windows/desktop/ms633588(v=vs.85).aspx
(2) http://msdn.microsoft.com/en-us/library/windows/desktop/ms633589(v=vs.85).aspx