Blender Git Loki

while checking weight paint code noticed that unified brush functions loop over the scenes to get the flag.
* this loop is called multiple times per vertex (not addressed in this commit)
* functions like brush_use_size_pressure(), brush_use_size_pressure() called unified_settings() twice when they didnt need to.

looks like this code cant work right with multiple scenes, added a comment on this - but at least avoid calling unified_settings() multiple times in single functions.