nptl: Move pthread_rwlock_init into libc

And __pthread_rwlock_init as a compatibility symbol.

__libc_rwlock_init is changed to call __pthread_rwlock_init directly.

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>