Code holiday commit:

- fix: user pref, window title was reset to 'Blender' on tab usage

- Undo history menu back:
  - name "Undo History"
  - hotkey alt+ctrl+z (alt+apple+z for mac)
  - works like 2.4x, only for global undo, editmode and particle edit.

- Menu scroll
  - for small windows or screens, popup menus now allow to display
    all items, using internal scrolling
  - works with a timer, scrolling 10 items per second when mouse 
    is over the top or bottom arrow
  - if menu is too big to display, it now draws to top or bottom, 
    based on largest available space.
  - also works for hotkey driven pop up menus.

- User pref "DPI" follows widget/layout size
  - widgets & headers now become bigger and smaller, to match 
    'dpi' font sizes. Works well to match UI to monitor size.
  - note that icons can get fuzzy, we need better mipmaps for it

source/blender/editors/util/util_intern.h

@@ -37,8 +37,12 @@
 /* internal exports only */
 
 /* editmode_undo.c */
-void undo_editmode_name(bContext *C, const char *undoname);
-int undo_editmode_valid(const char *undoname);
+void	undo_editmode_name			(struct bContext *C, const char *undoname);
+int		undo_editmode_valid			(const char *undoname);
+char	*undo_editmode_get_name		(struct bContext *C, int nr, int *active);
+void	*undo_editmode_get_prev		(struct Object *ob);
+void	undo_editmode_step			(struct bContext *C, int step);
+void	undo_editmode_number		(struct bContext *C, int nr);
 
 #endif /* ED_UTIL_INTERN_H */