title: pygtk: How to set the height of pop-up window in gtk.EntryCompletion
body: <p>I use gtk.EntryCompletion to implement the autocomletion function.
  But the list is so long that the pop-up window touches the bottom of screen.
  And I cant find the method of set the height of pop-up window in doc of pygtk.
  How to set the height of pop-up window in gtk.EntryCompletion?</p>