Basically this commit gets rid of most of the derived mesh immediate mode
drawing (cases such as subsurf excluded). Even when VBO is turned off
in user preferences, we still use vertex arrays, which are very similar to
VBOs but memory is client side. Vertex arrays are OpenGL 1.1 so compatibility
is not an issue here.
Reviewers: campbellbarton, sergey, jwilkins
Differential Revision: https://developer.blender.org/D919
2b7e1c6011