[Bf-taskforce25] Redrawing paint cursor during operators

[Nicholas Bishop]

The radial control operator (in wm_operators.c) should be able to use
the paint cursor overlay, but it seems that the paint cursor isn't
tagged for redraw when running in a modal operator. So in order to see
the redraw, the entire region is being marked (line 1108) This is all
making the radial control much slower on complex models.

-Nicholas