Problem: zmq_poller manpage is not build

Solution: add it to the makefile

doc/Makefile.am

@@ -16,7 +16,7 @@ MAN3 = zmq_bind.3 zmq_unbind.3 zmq_connect.3 zmq_disconnect.3 zmq_close.3 \
     zmq_proxy.3 zmq_proxy_steerable.3 \
     zmq_z85_encode.3 zmq_z85_decode.3 zmq_curve_keypair.3 zmq_curve_public.3 \
     zmq_has.3 \
-    zmq_timers.3 \
+    zmq_timers.3 zmq_poller.3 \
     zmq_atomic_counter_new.3 zmq_atomic_counter_set.3 \
     zmq_atomic_counter_inc.3 zmq_atomic_counter_dec.3 \
     zmq_atomic_counter_value.3 zmq_atomic_counter_destroy.3