Fix WiFiUDP::endPacket() return code, rev2 (#249)

Author: mjlitke

src/WiFiUdp.cpp

@@ -137,7 +137,7 @@ int WiFiUDP::endPacket()
 
 	int result = WiFiSocket.sendto(_socket, (void *)_sndBuffer, _sndSize, 0, (struct sockaddr *)&addr, sizeof(addr));
 
-	return (result <= 0) ? 0 : 1;
+	return (result < 0) ? 0 : 1;
 }
 
 size_t WiFiUDP::write(uint8_t byte)

src/utility/WiFiSocket.cpp

@@ -319,7 +319,7 @@ sint16 WiFiSocketClass::sendto(SOCKET sock, void *pvSendBuffer, uint16 u16SendLe
 	m2m_wifi_handle_events(NULL);
 
 	if (_info[sock].state != SOCKET_STATE_BOUND) {
-		return 0;
+		return -1;
 	}
 
 	return ::sendto(sock, pvSendBuffer, u16SendLength, flags, pstrDestAddr, u8AddrLen);