Blender Git Loki

Fix T41427: Region overlap moves into wrong window.

There was some fuzzyness in `region_overlap_fix()`, using an 'other side' region
as ref to move current one in case their rect would intersect...

New code is a bit more complex, but should handle nicely all situations, mostly
ensuring we only translate an overlap if we find a previous one **on the same side**,
and ensuring we also never have intersecting overlapping regions from different sides
(since this does not work nice at all).