Fixed NSMenu removeAllItems to also remove the cell views.

git-svn-id: svn+ssh://svn.gna.org/svn/gnustep/libs/gui/branches/gnustep_testplant_branch@38849 72102866-910b-0410-8b05-ffd578937521

Source/NSMenuView.m

@@ -559,6 +559,16 @@ static float menuBarHeight = 0.0;
   [self setNeedsDisplay: YES];
 }
 
+- (void) allItemsRemoved
+{
+  [self setHighlightedItemIndex: -1];
+  [_itemCells removeAllObjects];
+
+  // Mark the menu view as needing to be resized.
+  [self setNeedsSizing: YES];
+  [self setNeedsDisplay: YES];
+}
+
 /*
  * Working with Submenus.
  */