Blender Git Loki

View2D: More scroller related things

* Scrollers now keep corners free for drawing widgets if there are horizontal and vertical ones in use. They draw a rect which covers up all of the excess over-flowing drawing that was previously masked by the vertical scrollers.

* Tweaked the behaviour of the scroller zoom-handles again as they still weren't behaving correctly on vertical scrollers. This was partly caused by a typo, but also wrong checks...