2.5

Big commit, but mainly adminstration.

- Enabled ot->flag OPTYPE_UNDO to work.
- Removed all redundant ED_undo_pushes, but I'd
  recommend everyone to check it while testing. :)
- Added view manipulations as OPTYPE_REGISTER,
  although this will flood the redo stack a bit...
  Nevertheless; for a "redo last action" panel we
  can simply check if both flags are set for redo.

- Bugfix in editmode undo: selectmode was cleared,
  so you couldn't select after undo
- Bugfix in mixing tweaks and keymaps... solution
  works but is weak, need to think over a while.

source/blender/editors/space_node/node_header.c

@@ -147,8 +147,6 @@ void do_node_addmenu(bContext *C, void *arg, int event)
 	// XXX snode_autoconnect(snode, node, NODE_TEST);
 		
 	// XXX addqueue(curarea->win, UI_BUT_EVENT, B_NODE_TREE_EXEC);
-	
-	// ED_undo_push("Add Node");
 }
 
 static void node_make_addmenu(bContext *C, int nodeclass, uiBlock *block)