Blender Git Loki

- removed USE_CCGSUBSURF define (always on now)
- added G.editMesh->derived pointer... idea is to use this
for mesh derived from editmesh instead of Mesh->derived (as the
derived mesh tends to vary depending on what it came from).

This part could be cleaner, also there may problems with it not
being invalidated correctly.

- And most importantly: In case people were beginning to worry all
these edits were just crazy zr stuff, the big point comes about:
Incremental subsurf calculation is now enabled. This gives massive
speed improvements when editing a large mesh.

For the eye-candy happy: try setting G.rt==52 before entering editmode
and the edges and vertices (in optimal mode) will switch to displaying
visually the age since a region has last been calculated. Lots of
fun!