- added ModifierData flag, is modifier enabled in editmode

- added modifier type flag: should modifier be enabled by default for
   active in editmode
 - added subsurf "debug incremental" option instead of G.rt==52 (it becomes
   a slightly useful feature now for debugging how well a modifier works
   with incremental subsurf... maybe important for future python modifier
   developers)
 - shuffled modifier button layout just to keep people guessing
 - switched back to drawing editmesh face centers not through derivedmesh,
   I didn't think this one through, forgot that centers were also used for
   selection. have to think about what to do about this, should be either
   (a) don't draw centers with a cage active (optimal mode) or (b) come up
   with api to draw centers through derivedmesh and also handle selection.
 - changed recalc_editnormals to also follow the len(no)==0.0 use vertex
   co convention

source/blender/src/editmesh_lib.c

@@ -1370,7 +1370,10 @@ void recalc_editnormals(void)
 	}
 
 	for(eve= em->verts.first; eve; eve=eve->next) {
-		Normalise(eve->no);
+		if (Normalise(eve->no)==0.0) {
+			VECCOPY(eve->no, eve->co);
+			Normalise(eve->no);
+		}
 	}
 }