BMesh optimize face splitting by taking loops rather then verts

- add BM_vert_pair_share_face
- add BM_loop_is_adjacent
- remove BM_verts_connect
Cycles / Hair: No need to calculate curvepoint() when we use Ribbon curves.

Also some style cleanup.
Fix T37914: Mask modifier behaves differently until painted
UI: fix for slight glitch drawing image info

Using sub-pixel position made the text clip badly sometimes.
UI: Display alpha checkers in image info's color swatch.
Fix for own recent commit
Merge branch 'master' of http://git.blender.org/blender