FEATURES="userfetch" is now enabled by default. Depending on your ${DISTDIR}
 * permissions, this may result in Permission Denied errors. If you would like
 * to fetch with superuser privileges, add FEATURES="-userfetch" to make.conf.
 * 
 * The world file now supports slot atoms such as 'sys-devel/gcc:3.4'. In some
 * cases, emerge --depclean may remove slots that it would not have removed
 * in the past. The emerge --noreplace command can be used to add an atom to
 * the world file and prevent matching packages from being removed.  A slot
 * atom will be recorded in the world file for any atom that is precise enough
 * to identify a specific slot.
 * 
 * For help with using portage please consult the Gentoo Handbook
 * at http://www.gentoo.org/doc/en/handbook/handbook-x86.xml?part=3