bump(sys-libs/glibc): sync with upstream

glibc 2.16 has been marked stable upstream. By chance it also fixes
cross compiling header files in /usr/include/rpcsvc which should resolve
rpcbind's build failure searching for rpcsvc/mount.h. This previously
was not an issue because the hacky glibc install copied the files
directly from the host chroot into the target sysroot directories.