suggest: support zmq_msg_recv() in zmq >= 3

GitHub: refs #63

See also: http://www.zeromq.org/docs:3-1-upgrade

Reported by Naoya Inada. Thanks!!!

    groonga_suggest_learner.c:377:41: note: each undeclared identifier is reported only once for each function it appears in
    groonga_suggest_learner.c: In function ‘recv_event_loop’:
    groonga_suggest_learner.c:468:9: error: too few arguments to function ‘zmq_recv’
             if (zmq_recv(zmq_sock, &msg, 0)) {
             ^
    In file included from groonga_suggest_learner.c:17:0:
    /usr/include/zmq.h:350:16: note: declared here
     ZMQ_EXPORT int zmq_recv (void *s, void *buf, size_t len, int flags);
                    ^