Drivers Workflow: Change hotkey for "Add Drivers" to Ctrl-D (it was previously just DKEY)

Just using DKEY for this was resulting in too many drivers being accidentally created
by users drawing using Grease Pencil. This change also works better with the following
workflow changes to the driver setup process.

source/blender/editors/interface/interface_handlers.c

@@ -6978,12 +6978,12 @@ static int ui_do_button(bContext *C, uiBlock *block, uiBut *but, const wmEvent *
 		}
 		/* handle drivers */
 		else if ((event->type == DKEY) &&
-		         !IS_EVENT_MOD(event, shift, ctrl, oskey) &&
+		         !IS_EVENT_MOD(event, shift, oskey) &&
 		         (event->val == KM_PRESS))
 		{
 			if (event->alt)
 				ui_but_anim_remove_driver(C);
-			else
+			else if (event->ctrl)
 				ui_but_anim_add_driver(C);
 				
 			ED_region_tag_redraw(data->region);