Fix #34941: Space.draw_handler_add now supports PRE_VIEW and POST_VIEW callbacks
for more editors: timeline, graph, action, NLA, sequencer, image, clip.

git-svn-id: https://svn.blender.org/svnroot/bf-blender/trunk/blender@55937 954f8c5b-7b00-dc11-b283-0030488c597c