Blender uses 64bit atomics to manipulate SessionUUID, and these atomics
were not defined on any of 32bit platforms.
While official support is limited to 64bit platforms only, the code
should not make assumptions about bitness or endianess, in terms that
there should be codepaths and fallback (or provision of them) for 32bit
platforms.
This change makes 64bit atomic functions defined for all platforms.
The atomic_test was compiled and successfully tested on i686 and armv7l
platforms. The rest of compilation process of Blender will be very
tedious, so that was not done.
This change is essential, but not necessarily enough to make Blender
compilable on i686 (ability to compile Blender on 32bit platforms was
lost during the 2.91 development).
This is a functional part of original fix done by Brecht in D9577.
4a179e8e3e