nptl: Move pthread_rwlock_destroy into libc

And __pthread_rwlock_destroy as a compatibility symbol.

rwlocks do not need finalization, so change __libc_rwlock_fini to do
nothing.

The symbols were moved using scripts/move-symbol-to-libc.py.

Reviewed-by: Carlos O'Donell <carlos@redhat.com>
Tested-by: Carlos O'Donell <carlos@redhat.com>