Added clean target that deletes generated man pages

doc/Makefile.am

-MAN1 = zmq_forwarder.1 zmq_streamer.1 zmq_queue.1
+MAN1 = zmq_deviced.1
 MAN3 = zmq_bind.3 zmq_close.3 zmq_connect.3 zmq_init.3 \
     zmq_msg_close.3 zmq_msg_copy.3 zmq_msg_data.3 zmq_msg_init.3 \
     zmq_msg_init_data.3 zmq_msg_init_size.3 zmq_msg_move.3 zmq_msg_size.3 \
     zmq_poll.3 zmq_recv.3 zmq_send.3 zmq_setsockopt.3 zmq_socket.3 \
-    zmq_strerror.3 zmq_term.3 zmq_version.3 zmq_getsockopt.3 zmq_errno.3
+    zmq_strerror.3 zmq_term.3 zmq_version.3 zmq_getsockopt.3 zmq_errno.3 \
+    zmq_device.3
 MAN7 = zmq.7 zmq_tcp.7 zmq_pgm.7 zmq_epgm.7 zmq_inproc.7 zmq_ipc.7 \
     zmq_cpp.7
 MAN_DOC = $(MAN1) $(MAN3) $(MAN7)
@@ -26,6 +27,8 @@ MAINTAINERCLEANFILES = $(MAN_DOC) $(MAN_HTML)
 
 dist-hook : $(MAN_DOC) $(MAN_HTML)
 
+clean:
+	rm *.1 *.3 *.7
 if BUILD_DOC
 SUFFIXES=.html .txt .xml .1 .3 .7