Added up/down arrow to combo box.

  The interface to comboboxes has been enhanced by allowing certain
keyboard input in a dropdown or dropdown-list combobox. You can use
the UP and DOWN arrow keys to scroll through the available choices
in a combo box. You can also use the HOME, END, PGUP and PGDN keys
to move to the start, to the end, up one page, or down one page of
choices.
  You can now set the focus to a combobox by tabbing to it.