gtk-2.0/img/frame_*.png: (m) fix (added forgoten images)
gtk-2.0/gtkrc: 0.16.8 version bump (column-header update)
gtk-3.0/{common,gtk}.css: 0.16.8 version bump (column-header, GtkTreeView and GtkNotebook update)
gtk-3.0/{common,gtk}.css: update (row)
ChangeLog README.md: 0.16.8 version bump
ChangeLog: update