Blender Git Loki

De-duplicate large block of shared code for GL vert attribs

Code in ccgdm_draw_attrib_vertex() was entirely the same as the top
portion of the code in cddm_draw_attrib_vertex(). Moved this code to a
new function, DM_draw_attrib_vertex().

ccgdm_draw_attrib_vertex() was removed in favor of calling
DM_draw_attrib_vertex(). cddm_draw_attrib_vertex() still does a couple
extra things, so it still exists but calls DM_draw_attrib_vertex().

In the interest of easy code review, no changes made to the code in
DM_draw_attrib_vertex() other than the new name and an added comment.

Reviewers: campbellbarton

Differential Revision: https://developer.blender.org/D1010