Fix evil own bug: paint_redraw accessed freed memory. Still doesn't
solve problem not being able to paint with black in image editor.


git-svn-id: https://svn.blender.org/svnroot/bf-blender/trunk/blender@55355 954f8c5b-7b00-dc11-b283-0030488c597c
Feature:

Image Editor and 3D view background image now use new automatic switching for
drawing GPU texture or OpenGL DrawPixels too. For large zoomed images
it gives massive speedup.



git-svn-id: https://svn.blender.org/svnroot/bf-blender/trunk/blender@55356 954f8c5b-7b00-dc11-b283-0030488c597c