Blender Git Loki

Memory allocation: do not use mmap for memory allocation on 64 bit.

On Windows we can only do mmap memory allocation up to 4 GB, which causes a
crash when doing very large renders on 64 bit systems with a lot of memory.

As far as I can tell the reason to use mmap is to get around address space
limitation on some 32 bit operating systems, and I can't see a reason to use
it on 64 bit. For the original explanation see here:
http://orange.blender.org/blog/stupid-memory-problems

Fixes T37841.