Add ability to change port nproxy listens on.

pdns-3.1-nproxyport.patch

diff -ur pdns-3.1.orig/pdns/nproxy.cc pdns-3.1.nproxyport/pdns/nproxy.cc
--- pdns-3.1.orig/pdns/nproxy.cc	2012-05-04 06:13:23.000000000 -0400
+++ pdns-3.1.nproxyport/pdns/nproxy.cc	2012-07-13 10:00:47.394599792 -0400
@@ -198,6 +198,7 @@
     ("setgid", po::value<int>(), "setgid to this numerical user id")
     ("origin-address", po::value<string>()->default_value("::"), "Source address for notifications to PowerDNS")
     ("listen-address", po::value<vector<string> >(), "IP addresses to listen on")
+    ("listen-port", po::value<int>(), "Port to listen on")
     ("daemon,d", po::value<bool>()->default_value(true), "operate in the background")
     ("verbose,v", "be verbose");
 
@@ -224,11 +225,17 @@
   else
     addresses.push_back("::");
 
+  int lport;
+  if(g_vm.count("listen-port"))
+    lport=g_vm["listen-port"].as<int>();
+  else
+    lport=53;
+
   // create sockets to listen on
   
   syslogFmt(boost::format("Starting up"));
   for(vector<string>::const_iterator address = addresses.begin(); address != addresses.end(); ++address) {
-    ComboAddress local(*address, 53);
+    ComboAddress local(*address, lport);
     int sock = socket(local.sin4.sin_family, SOCK_DGRAM, 0);
     if(sock < 0)
       throw runtime_error("Creating socket for incoming packets: "+stringerror());