Blender Git Loki

Atomic ops: Fix atomic_add_uint32 and atomic_sub_uint32 in Windows

The assembler version in Windows used to return the previous value
of the variable while all the other versions return the new value.
This is now fixed for consistency.
Note: this bug had no effect on blender because no part of the code
use the return value of these functions, but the future BGE DeckLink
module makes use of it to implement reference counter.