Blender Git Loki

Bugfix, irc collection:

With larger header sizes (via DPI setting), splitting an area horizontally (using
left-bottom corner widget, move up) stopped immediate after split, not allowing
to drag it to a position.

Culprit was code to check minimum header size, and area operator using the same
flags. Now ScrVert has two flags - one for internal use, one for the tools to set.