[Pixman] Building as 64-Bit (i.e. dropping the use of USE_X86_MMX )

[John Emmas]

Hi there - hopefully this'll be a simple one...

I've been building pixman-1 (from git) for many years, using MSVC - but 
until now I'd only ever built as 32-bit.  This morning I tried switching 
to a 64-bit build (with VS2019) and I've hit a small problem which 
basically comes down to me using the #define USE_X86_MMX

Understandably, USE_X86_MMX doesn't work for a 64-bit build.  I assumed 
there might be a 64-bit alternative (USE_X64_MMX) but that doesn't seem 
to exist  :-(

So do I just need to stop #defining USE_X86_MMX now?  Or is there some 
alternative #define that I'll need to use instead?

Thanks, John