#19343: vertex paint blur was not working. shared vcol was disabled
for speed, but blurring still needs it. Also fixed brushes with
size > 64 not working correct.
#19314: non-zbuffer selection did not work with background image,
drawing it made the WM matrix go out of sync.
Forgot to mention these in previous commit:
* Manipulator type was not properly initialized, .B.blend update helps,
but still needed version patch & correct setting for new space.
* Added a utility function for the toggling region hide, instead of
duplicating the code.
* SSS preview render preprocessing pass now also uses multiple threads.
* Added version patch for unit scale, was still 0.0.
f302ebeb67