Problem: wildcard address with udp not mentioned

* UDP is mentioned as available transport, and it also supports
  wildcard addresses, but not mentioned
* zmq_unbind(7) also mentions about wild-card endpoint in zmq_bind(3)

Solution: add udp in wildcard address related docs

doc/zmq_bind.txt

@@ -34,8 +34,9 @@ Every 0MQ socket type except 'ZMQ_PAIR' supports one-to-many and many-to-one
 semantics. The precise semantics depend on the socket type and are defined in
 linkzmq:zmq_socket[3].
 
-The 'ipc', 'tcp' and 'vmci' transports accept wildcard addresses: see linkzmq:zmq_ipc[7],
-linkzmq:zmq_tcp[7] and linkzmq:zmq_vmci[7] for details.
+The 'ipc', 'tcp', 'vmci' and 'udp' transports accept wildcard addresses: see
+linkzmq:zmq_ipc[7], linkzmq:zmq_tcp[7], linkzmq:zmq_vmci[7] and
+linkzmq:zmq_udp[7] for details.
 
 NOTE: the address syntax may be different for _zmq_bind()_ and _zmq_connect()_
 especially for the 'tcp', 'pgm' and 'epgm' transports.

doc/zmq_unbind.txt

@@ -28,9 +28,9 @@ The 'endpoint' argument is as described in linkzmq:zmq_bind[3]
 Unbinding wild-card address from a socket
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 When wild-card `*` 'endpoint' (described in linkzmq:zmq_tcp[7],
-linkzmq:zmq_ipc[7] and linkzmq:zmq_vmci[7]) was used in _zmq_bind()_, the caller should use
-real 'endpoint' obtained from the ZMQ_LAST_ENDPOINT socket option
-to unbind this 'endpoint' from a socket.
+linkzmq:zmq_ipc[7], linkzmq:zmq_udp[7] and linkzmq:zmq_vmci[7]) was used in
+_zmq_bind()_, the caller should use real 'endpoint' obtained from the 
+ZMQ_LAST_ENDPOINT socket option to unbind this 'endpoint' from a socket.
 
 RETURN VALUE
 ------------