Update code for checking for libffi on windows.  Mingw will use ffi while VC++ will use libffi.  Also don't add in GNU makefile when on windows.
Update code for checking for libffi on windows.  Mingw will use ffi while VC++ will use libffi.  Also don't add in GNU makefile when on windows.

ferventcoder/ffi,sparkchaser/ffi,yghannam/ffi,ferventcoder/ffi,majioa/ffi,mvz/ffi,sparkchaser/ffi,MikaelSmith/ffi,majioa/ffi,MikaelSmith/ffi,yghannam/ffi,sparkchaser/ffi,yghannam/ffi,tduehr/ffi,ferventcoder/ffi,tduehr/ffi,ffi/ffi,yghannam/ffi,mvz/ffi,mvz/ffi,tduehr/ffi,MikaelSmith/ffi,sparkchaser/ffi,ffi/ffi,mvz/ffi,majioa/ffi,majioa/ffi,yghannam/ffi,ferventcoder/ffi,MikaelSmith/ffi,ffi/ffi,tduehr/ffi