created readme file for PIC port.

bacnet-stack/ports/pic18/readme.txt

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+BACnet Stack - SourceForge.net
+Build for MPLAB IDE
+
+These are some settings that are important when building 
+the BACnet Stack using MPLAB IDE and MCC18 Compiler,
+
+1. Add the files to the project that you need:
+abort.c, apdu.c, bacapp.c, bacdcode.c, bacerror.c,
+bacstr.c, bigend.c, crc.c, datalink.c, dcc.c, dlmstp.c,
+ima.c, mstp.c, npdu.c, rd.c, reject.c, reject.c,
+ringbuf.c, rp.c, whois.c, wp.c
+
+From demo/object/: device.c or dev_tiny.c, ai.c, ao.c, etc.
+
+From demo/handler/: h_dcc.c, h_rd.c, h_rp.c, h_wp.c
+
+2. Project->Options->Project
+
+General Tab: Include Path:
+C:\code\bacnet-stack\;C:\code\bacnet-stack\demo\handler\;C:\code\bacnet-stack\demo\object\;C:\code\bacnet-stack\ports\pic18\
+
+MPLAB C18 Tab: Memory Model:
+Code: Large Code Model
+Data: Large Data Model
+Stack: Multi-bank Model
+
+MPLAB C18 Tab: General: Macro Definitions:
+PRINT_ENABLED=0
+BACDL_MSTP
+BIG_ENDIAN=1