sendrecvmsg_shutdown function moved to mshutdown

The function php_socket_sendrecvmsg_shutdown() should have been called in
MSHUTDOWN, not RSHUTDOWN.

Bug only on TSRM builds.

Should fix bug #64287.
Merge branch 'PHP-5.5'

* PHP-5.5:
  sendrecvmsg_shutdown function moved to mshutdown