add DEFAULT_UPNP constant in net

- as this is a shared Core/GUI setting, this makes it easier to keep them
  in sync (also no new includes are needed)

src/net.cpp

@@ -1736,10 +1736,8 @@ void StartNode(boost::thread_group& threadGroup)
     else
         threadGroup.create_thread(boost::bind(&TraceThread<void (*)()>, "dnsseed", &ThreadDNSAddressSeed));
 
-#ifdef USE_UPNP
     // Map ports with UPnP
-    MapPort(GetBoolArg("-upnp", USE_UPNP));
-#endif
+    MapPort(GetBoolArg("-upnp", DEFAULT_UPNP));
 
     // Send and receive from sockets, accept connections
     threadGroup.create_thread(boost::bind(&TraceThread<void (*)()>, "net", &ThreadSocketHandler));

src/net.h

@@ -38,6 +38,12 @@ namespace boost {
 
 /** The maximum number of entries in an 'inv' protocol message */
 static const unsigned int MAX_INV_SZ = 50000;
+/** -upnp default */
+#ifdef USE_UPNP
+static const bool DEFAULT_UPNP = USE_UPNP;
+#else
+static const bool DEFAULT_UPNP = false;
+#endif
 
 inline unsigned int ReceiveFloodSize() { return 1000*GetArg("-maxreceivebuffer", 5*1000); }
 inline unsigned int SendBufferSize() { return 1000*GetArg("-maxsendbuffer", 1*1000); }

src/qt/optionsmodel.cpp

@@ -106,11 +106,7 @@ void OptionsModel::Init()
 
     // Network
     if (!settings.contains("fUseUPnP"))
-#ifdef USE_UPNP
-        settings.setValue("fUseUPnP", true);
-#else
-        settings.setValue("fUseUPnP", false);
-#endif
+        settings.setValue("fUseUPnP", DEFAULT_UPNP);
     if (!SoftSetBoolArg("-upnp", settings.value("fUseUPnP").toBool()))
         addOverriddenOption("-upnp");