LinkConfiguration: use qobject_cast instead of dynamic_cast

qobject_cast is times faster dynamic_cast for objects that
inherit QObject. also, use auto keyword to not duplicate
class names.

src/comm/LinkConfiguration.cc

@@ -118,26 +118,26 @@ LinkConfiguration* LinkConfiguration::duplicateSettings(LinkConfiguration* sourc
     switch(source->type()) {
 #ifndef NO_SERIAL_LINK
         case TypeSerial:
-            dupe = new SerialConfiguration(dynamic_cast<SerialConfiguration*>(source));
+            dupe = new SerialConfiguration(qobject_cast<SerialConfiguration*>(source));
             break;
 #endif
         case TypeUdp:
-            dupe = new UDPConfiguration(dynamic_cast<UDPConfiguration*>(source));
+            dupe = new UDPConfiguration(qobject_cast<UDPConfiguration*>(source));
             break;
         case TypeTcp:
-            dupe = new TCPConfiguration(dynamic_cast<TCPConfiguration*>(source));
+            dupe = new TCPConfiguration(qobject_cast<TCPConfiguration*>(source));
             break;
 #ifdef QGC_ENABLE_BLUETOOTH
         case TypeBluetooth:
-            dupe = new BluetoothConfiguration(dynamic_cast<BluetoothConfiguration*>(source));
+            dupe = new BluetoothConfiguration(qobject_cast<BluetoothConfiguration*>(source));
             break;
 #endif
         case TypeLogReplay:
-            dupe = new LogReplayLinkConfiguration(dynamic_cast<LogReplayLinkConfiguration*>(source));
+            dupe = new LogReplayLinkConfiguration(qobject_cast<LogReplayLinkConfiguration*>(source));
             break;
 #ifdef QT_DEBUG
         case TypeMock:
-            dupe = new MockConfiguration(dynamic_cast<MockConfiguration*>(source));
+            dupe = new MockConfiguration(qobject_cast<MockConfiguration*>(source));
             break;
 #endif
         case TypeLast: