MAVLink: Update complete app to support MAVLink 1 & MAVLink 2. Add MAV_PROTO_VER param to switch between them

src/modules/mavlink/mavlink_params.c

@@ -47,6 +47,15 @@ PARAM_DEFINE_INT32(MAV_SYS_ID, 1);
  */
 PARAM_DEFINE_INT32(MAV_COMP_ID, 1);
 
+/**
+ * MAVLink protocol version
+ * @group MAVLink
+ * @value 0 Default to 1, switch to 2 if GCS sends version 2
+ * @value 1 Always use version 1
+ * @value 2 Always use version 2
+ */
+PARAM_DEFINE_INT32(MAV_PROTO_VER, 1);
+
 /**
  * MAVLink Radio ID
  *