fix implicit declaration warnings for pthread_set_name_np on OpenBSD (#1425)
fix implicit declaration warnings for pthread_set_name_np on OpenBSD (#1425)

OpenBSD requires an additional header for both pthread_set_name_np and
pthread_get_name_np.

See http://man.openbsd.org/pthread_set_name_np for details.
nanomsg/nng,nanomsg/nng,nanomsg/nng,nanomsg/nng