deimos ~ # emerge world -upvDN

These are the packages that would be merged, in order:

Calculating world dependencies -
!!! Ebuilds for the following packages are either all
!!! masked or don't exist:
xfce-extra/xfce4-artwork

... done!
[ebuild     U ] dev-libs/nspr-4.6.5-r1 [4.6.3] USE="ipv6 -debug%" 1,255 kB 
[ebuild     U ] dev-libs/nss-3.11.5 [3.11.3] 3,611 kB 

Total: 2 packages (2 upgrades), Size of downloads: 4,865 kB