Feature/makefile add apps library (#218)

* add BACnet stack library at apps/lib

* convert apps to use apps/lib for smaller binary

* fix -DBACDL_ALL=1 build

* fix piface build

* datalink MAX_MPDU and MAX_HEADER cleanup

* add bip6 to git workflow

* fix system library dependency of BACnet library

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

ports/pic18f97j60/mstp.h

@@ -148,7 +148,7 @@ struct mstp_port_struct_t {
 
     /* An array of octets, used to store PDU octets prior to being transmitted. */
     /* This array is only used for APDU messages */
-    uint8_t TxBuffer[MAX_MPDU];
+    uint8_t TxBuffer[DLMSTP_MPDU_MAX];
     unsigned TxLength;
     uint8_t TxDestination;
     bool TxReady;       /* true if ready to be sent or received */