Problem: documentation for zmq_udp is outdated

Solution: update to document new binding options and IPv6 support

doc/zmq_udp.txt

@@ -37,11 +37,12 @@ colon and the UDP port number to use.
 An 'interface' may be specified by either of the following:
 
 * The wild-card `*`, meaning all available interfaces.
-* The primary IPv4 address assigned to the interface, in its numeric
-  representation.
+* The name of the network interface (i.e. eth0, lo, wlan0 etc...)
+* The primary address assigned to the interface, in its numeric representation.
 * Multicast address in its numeric representation the socket should join.
 
-The UDP port number may be specified a numeric value, usually above 1024 on POSIX systems.
+The UDP port number may be specified a numeric value, usually above
+1024 on POSIX systems.
 
 Connecting a socket
 ~~~~~~~~~~~~~~~~~~~
@@ -52,7 +53,8 @@ a colon and the UDP port number to use.
 
 A 'peer address' may be specified by either of the following:
 
-* The IPv4 or IPv6 address of the peer, in its numeric representation.
+* The IPv4 or IPv6 address of the peer, in its numeric representation
+  or using its hostname.
 * Multicast address in its numeric representation.
 
 EXAMPLES
@@ -65,9 +67,18 @@ assert (rc == 0);
 //  Unicast - UDP port 5555 on the local loop-back interface
 rc = zmq_bind(dish, "udp://127.0.0.1:5555");
 assert (rc == 0);
+//  Unicast - UDP port 5555 on interface eth1
+rc = zmq_bind(dish, "udp://eth1:5555");
+assert (rc == 0);
 //  Multicast - UDP port 5555 on a Multicast address
 rc = zmq_bind(dish, "udp://239.0.0.1:5555");
 assert (rc == 0);
+//  Same as above but joining only on interface eth0
+rc = zmq_bind(dish, "udp://eth0;239.0.0.1:5555");
+assert (rc == 0);
+//  Same as above using IPv6 multicast
+rc = zmq_bind(dish, "udp://eth0;[ff02::1]:5555");
+assert (rc == 0);
 ----
 
 
@@ -76,9 +87,15 @@ assert (rc == 0);
 //  Connecting using an Unicast IP address
 rc = zmq_connect(radio, "udp://192.168.1.1:5555");
 assert (rc == 0);
-//  Connecting using a Multicast address"
+//  Connecting using a Multicast address
 rc = zmq_connect(socket, "udp://239.0.0.1:5555);
 assert (rc == 0);
+//  Connecting using a Multicast address using local interface wlan0
+rc = zmq_connect(socket, "udp://wlan0;239.0.0.1:5555);
+assert (rc == 0);
+//  Connecting to IPv6 multicast
+rc = zmq_connect(socket, "udp://[ff02::1]:5555);
+assert (rc == 0);
 ----