Blender Git Loki

View2D: Code cleanup - UI_view2d_status_enforce()

This commit *should* bring UI_view2d_status_enforce() (formerly known in pre 2.5 as test_view2d) under control again.
I've attempted to reduce the amount of duplicated code here, so hopefully there won't be any nasty bugs that will show up in some of the other views when they are ported.

Summary of changes:
* Restored V2D_KEEPZOOM flag which I had previously removed, having misunderstood its function.
* Fixed bugs with resizing Outliner window
* Outliner width is now columns + 1 again. Documented reasons for this (otherwise, stuff gets covered by scrollbars, but we cannot see it)