Optimize face-select drawing (weight/vertex paint mode face selection) 
with bmesh theres no need for edge-hash lookups, replace EdgeHash with BLI_bitmap.


git-svn-id: https://svn.blender.org/svnroot/bf-blender/trunk/blender@56697 954f8c5b-7b00-dc11-b283-0030488c597c