mips and ppc64: As of 2.16.2, gdm has a dep on gksu so that the menu entry for gdmsetup works for normal users. You don't have gksu keyworded, so I've dropped your keywords for now. Please keyword x11-libs/gksu and x11-libs/libgksu ~arch, and then restore your keywords on gnome-base/gdm-2.16.2
thanks! added ~ppc64
All done here.