Enable SSE2 for win32

XBMC 12.0, 12.1 and 12.2 were already released. All of them include AE and SSE2 heavily used in AE (look for __m128i in code).
I don't see any reason to have SSE2 enabled only for one core part of XBMC, so this PR enables SSE2 for all VC-compiled XBMC projects.