[Bf-codereview] Drag to close areas (issue 6269044)

[brechtvanlommel at gmail.com]

When you drag down the top info header (to view reports), and then drag
it back up, weird things happen, and the outliner header also gets
hidden partially but snaps back when you move the mouse into the
outliner editor.

That's an example of a case that wouldn't be allowed to be close with
dragging the handles, but further, there's also a more general conflict
here. Some users will drag down an editor to just the size of the
header, to move it out of the way temporarily but not close it. With
this change it's not possible anymore to do this.

http://codereview.appspot.com/6269044/