Add core stack headers into bacdef.h and cleanup includes. (#602)

* Added dependent BACnet stack headers into bacdef.h file.

* Changed bacdef.h and other stack includes in c/h files to have a common pattern.

* Moved bits.h, bytes.h, and bacnet_stack_exports.h under bacnet/basic/sys/ folder.

ports/atmega168/apdu.c

@@ -34,11 +34,11 @@
 #include <stdbool.h>
 #include <stdint.h>
 #include <stddef.h>
-#include "bacnet/bits.h"
-#include "bacnet/apdu.h"
+/* BACnet Stack defines - first */
 #include "bacnet/bacdef.h"
+/* BACnet Stack API */
+#include "bacnet/apdu.h"
 #include "bacnet/bacdcode.h"
-#include "bacnet/bacenum.h"
 #include "bacnet/basic/services.h"
 
 bool apdu_service_supported(BACNET_SERVICES_SUPPORTED service_supported)

ports/atmega168/dlmstp.c

@@ -36,18 +36,19 @@
 #include <stdint.h>
 #include <stddef.h>
 #include <string.h>
+/* BACnet Stack defines - first */
 #include "bacnet/bacdef.h"
+/* BACnet Stack API */
 #include "bacnet/datalink/mstpdef.h"
 #include "bacnet/datalink/dlmstp.h"
-#include "rs485.h"
 #include "bacnet/datalink/crc.h"
 #include "bacnet/npdu.h"
-#include "bacnet/bits.h"
-#include "bacnet/bytes.h"
 #include "bacnet/bacaddr.h"
 /* special optimization - I-Am response in this module */
 #include "bacnet/basic/services.h"
 #include "bacnet/basic/tsm/tsm.h"
+/* port specific */
+#include "rs485.h"
 
 /* This file has been customized for use with small microprocessors */
 /* Assumptions:

ports/atmega168/hardware.h

@@ -38,6 +38,6 @@
 #endif
 #endif
 #include "iar2gcc.h"
-#include "bacnet/bits.h"
+#include "bacnet/basic/sys/bits.h"
 
 #endif