This deduplicates/simplifies some code. Also cleanup up a bit scopes UI code!
Use new GRIP button for uiList grab-resize.
This allows us to greatly simplifies the code, and get rid of a few hacks in uiList event handling!
Note autosize mode of uiList is now trigered by any value of list_grip below a given threshold, rather than the fixed zero value...
Reviewers: brecht
Reviewed By: brecht
Differential Revision: https://developer.blender.org/D343