GTK+ 2.16.4 stable release

This is a quick followup release to fix an unfortunate bug that was introduced in 2.16.3.
This fixes a side-effect introduced by the fix for bug 586330 that caused all stock buttons to loose their mnemonics.

See the original announcement for more info and downloads.

Author: andreasn

GNOME Artist based in Gothenburg, Sweden. Working at Imendio AB.