Enable SSE Intrinistics on MSVC 2013+ 32-bit Builds

Use __vectorcall on  graphene_simd4x4f_init() on MSVC 2013 (and later)
32-bit builds so that SSE intrinistics can be enabled on 32-bit builds for
recent MSVC versions.  Also, as Emmanuele suggested, move the VECTORCALL
macro definition into graphene-macros.h.