Blender Git Loki

Fix T42653, solidify modifier not displaying correctly under edit mode.

Basically, our drawing code assumed we always use the edit mesh
materials, which can be different from the derived mesh
materials in modifiers doing overrides. We usually we want to use the
derived mesh when it is available instead.

There are two fixes here for both solid and textured mode. Unfortunately
the fixes do not help to make the display code less labyrinthian but I
expect this "should work" (tm and famous last words)

Solid mode fix is 95% from Bastien, thanks!