Fix -Wsign-compare and -Wtype-limits

src/comm/QGCJSBSimLink.cc

@@ -241,8 +241,7 @@ void QGCJSBSimLink::readBytes()
 
         // Echo data for debugging purposes
         std::cerr << __FILE__ << __LINE__ << "Received datagram:" << std::endl;
-        int i;
-        for (i=0; i<s; i++)
+        for (unsigned int i=0; i<s; i++)
         {
             unsigned int v=data[i];
             fprintf(stderr,"%02x ", v);

src/ui/MAVLinkDecoder.cc

@@ -87,7 +87,7 @@ void MAVLinkDecoder::receiveMessage(LinkInterface* link,mavlink_message_t messag
     time = getUnixTimeFromMs(message.sysid, time);
 
     // Send out all field values for this message
-    for (int i = 0; i < messageInfo[msgid].num_fields; ++i)
+    for (unsigned int i = 0; i < messageInfo[msgid].num_fields; ++i)
     {
         emitFieldValue(&message, i, time);
     }