Fix/workaround for GLSL textured and matcap modes for dyntopo

Currently used special checks in DM draw code, perhaps better would be
simply to flush changes from PBVH to DM.

Anyway, now things seems to be working OK, will check on better solution
from code point of view later.

git-svn-id: https://svn.blender.org/svnroot/bf-blender/trunk/blender@54002 954f8c5b-7b00-dc11-b283-0030488c597c