Here is my second attempt at T43389.
What I have placed in the diffs is the following:
- Added vertex selection mode (next to face selection) (view3d_header.c)
- A few fixes to make vertex selection doable with RMB (drawobject.c, paint.c)
- Enabled the Assign/Remove, Select/Deselect buttons on the vertex group panel (object_vgroup.c and properties_data_mesh.py)
In the original request the buttons Assign/remove were't mentioned but I think it make sense to have them too (and t's even easier to implement).
All this in Vertex Paint mode. I left out Texture Paint.