Blender Git Loki

Fix a few DPI / retina draw issues:

* Color picker cursor was too small, and color cirle was not smooth enough.
* Border select gesture cross before first click did not reach to the border
of the window.
* Buttons were not drawing emboss properly (also for non-retina actually).
Note it doesn't draw entirely right for aligned buttons, but this was also
the case before it got broken.