update LwIP BACnet/IP abstraction (#246)

* update LwIP BACnet/IP abstraction. Integrate LwIP build with continuous integration.

Co-authored-by: Steve Karg <skarg@users.sourceforge.net>

ports/lwip/bacport.h

@@ -0,0 +1,39 @@
+/**************************************************************************
+*
+* Copyright (C) 2020 Steve Karg <skarg@users.sourceforge.net>
+*
+* Permission is hereby granted, free of charge, to any person obtaining
+* a copy of this software and associated documentation files (the
+* "Software"), to deal in the Software without restriction, including
+* without limitation the rights to use, copy, modify, merge, publish,
+* distribute, sublicense, and/or sell copies of the Software, and to
+* permit persons to whom the Software is furnished to do so, subject to
+* the following conditions:
+*
+* The above copyright notice and this permission notice shall be included
+* in all copies or substantial portions of the Software.
+*
+* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
+* IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
+* CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
+* TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
+* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+*
+*********************************************************************/
+
+#ifndef BACPORT_H
+#define BACPORT_H
+
+#include <stdint.h>
+#include <stdbool.h>
+#include <string.h>
+#include "lwip/def.h"
+#include "lwip/udp.h"
+#include "lwip/memp.h"
+#include "netif/etharp.h"
+#include "lwip/dhcp.h"
+#include "lwip/inet.h"
+
+#endif