Bugfix #25652

Report was that move-to-layer menu failed. The real cause was
more complex; had to dive deep in the dungeons of the interface
code that handled undos and operators. Found several issues:

- popup menus (like redo operator, color picker) executed again
  on a mouse-exit
- far too many buttons were sending undo pushes; even worse, in
  the operator redo-panel each button action was pushed twice
- in case operator redo-buttons have own callbacks (like layer
  buttons) the redo wasn't working
- layerbutton menu was called without creating a proper undo/redo
  case

Things should all work smoother now!

On todo:
- better definition and handling of all versions for operator menus
  (four types now, not fun)
  also: make operator "do" menu, which on first action does operator
  and then switches to redo-ing
- bring back Undo menu, to list the undo stack and jump in it.

source/blender/editors/include/UI_interface.h

@@ -211,6 +211,7 @@ typedef struct uiLayout uiLayout;
 #define TOGBUT		(37<<9)
 #define OPTION		(38<<9)
 #define OPTIONN		(39<<9)
+		/* buttons with value >= SEARCH_MENU don't get undo pushes */
 #define SEARCH_MENU	(40<<9)
 #define BUT_EXTRA	(41<<9)
 #define HSVCIRCLE	(42<<9)