- 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!

source/blender/blenkernel/intern/displist.c

@@ -1775,7 +1775,7 @@ void makeDispList(Object *ob)
 
 		if (mesh_uses_displist(me)) {  /* subsurf */
 			if (ob==G.obedit) {
-				me->derived= subsurf_make_derived_from_editmesh(em, me->subdiv, me->subsurftype);
+				G.editMesh->derived= subsurf_make_derived_from_editmesh(em, me->subdiv, me->subsurftype, G.editMesh->derived);
 			} else {
 				me->derived= subsurf_make_derived_from_mesh(me, me->subdiv);
 			}