Blender Git Loki

Fix T45389 Windows thumbnails not working.

Also they did not work when using blender -R from
command line in 64-bit systems.
Issue was checking for wrong define which would
cause code to detect if the blender executable
functions under 32 bit emulation.
For 64bit executables this is false, leading
blender to believe we are operating under a 32bit
system, and registration would try to register
the 32bit thumbnailer.

This 32 bit dll is (correctly) missing for local
installs and from the new installer, thus no thumbnails.