SITL: add multi-vehicle support to rcS

This also removes the HIGHRES_IMU mavlink stream to the GCS. I don't see
why it's needed and it adds noticeable CPU load.

src/modules/simulator/simulator.cpp

@@ -142,7 +142,7 @@ void Simulator::parameters_update(bool force)
 int Simulator::start(int argc, char *argv[])
 {
 	int ret = 0;
-	int udp_port = 0;
+	int udp_port = 14560;
 	_instance = new Simulator();
 
 	if (_instance) {

src/modules/simulator/simulator_mavlink.cpp

@@ -669,12 +669,6 @@ void Simulator::pollForMAVLinkMessages(bool publish, int udp_port)
 	// udp socket data
 	struct sockaddr_in _myaddr;
 
-	if (udp_port < 1) {
-		int32_t prt;
-		param_get(param_find("SITL_UDP_PRT"), &prt);
-		udp_port = prt;
-	}
-
 	// try to setup udp socket for communcation with simulator
 	memset((char *)&_myaddr, 0, sizeof(_myaddr));
 	_myaddr.sin_family = AF_INET;

src/modules/simulator/simulator_params.c

@@ -40,13 +40,6 @@
  */
 #include <parameters/param.h>
 
-/**
- * Simulator UDP port
- *
- * @group SITL
- */
-PARAM_DEFINE_INT32(SITL_UDP_PRT, 14560);
-
 /**
  * Simulator Battery drain interval
  *