Blender Git Loki

2.5: gesture code in WM

- Simplified and cleaned previous border code
It was a bit too complex, too many data manipulations

Original idea was to have WM API calls to manage border, circle, lines,
lasso, etc. This now means that WM provides callbacks for custom operators,
so it's very easy to make them. Check bottom of screen_edit.c for an
example.

Currently two borders were coded; with and without cross hair.
Press Bkey in any area-region to test it (note: time window has wrong matrix!)

Some specs to note:
- gestures are in region space, and draw 'over'. That latter still needs some
work when we do real composites.
- only the active region is redrawn.
- on todo is the generic gesture engine for 'tweak' or like how currently grab
gestures in Blender work. These will be configurable per area-region, and WM
then will send the proper "Gesture Event" with properties (N, S, E, W, etc)
to which you then can assign operators. Such events will be generated with low
priority, so other handlers who swallowed mouse events have preference.