Mark places that might want changing for IPv6.

Any places which I feel might want to be updated to work differently
with IPv6 have been marked with a comment starting "IPV6:".

Currently the only comments address places where an IP address is
combined with a port using the standard : separated form. These may want
to be changed when printing IPv6 addresses to wrap the address in []
such as

	[2001:db8::c0:ffee]:6379

instead of

	2001:db8::c0:ffee:6379

as the latter format is a technically valid IPv6 address and it is hard
to distinguish the IPv6 address component from the port unless you know
the port is supposed to be there.

src/cluster.c

@@ -317,6 +317,7 @@ void clusterAcceptHandler(aeEventLoop *el, int fd, void *privdata, int mask) {
         redisLog(REDIS_VERBOSE,"Accepting cluster node: %s", server.neterr);
         return;
     }
+    /* IPV6: might want to wrap a v6 address in [] */
     redisLog(REDIS_VERBOSE,"Accepted cluster node %s:%d", cip, cport);
     /* We need to create a temporary node in order to read the incoming
      * packet in a valid contest. This node will be released once we

src/networking.c

@@ -1216,6 +1216,7 @@ void clientCommand(redisClient *c) {
 
             client = listNodeValue(ln);
             if (anetPeerToString(client->fd,ip,sizeof(ip),&port) == -1) continue;
+            /* IPV6: might want to wrap a v6 address in [] */
             snprintf(addr,sizeof(addr),"%s:%d",ip,port);
             if (strcmp(addr,c->argv[2]->ptr) == 0) {
                 addReply(c,shared.ok);