bump(sys-libs/pam): Import current stable pam from Gentoo
fix(sys-libs/pam): Remove libs from /lib64

This ebuild calls gen_usr_ldscript to move libraries from /usr to / and
then symlinks to them from /usr. Clear all that crap out and use /usr.
Merge pull request #278 from marineam/symlink-usr

pam /usr fixes