Long lost RISC OS 3.10 patch, recovered by mechanical disassembly.
Builds a binary identical module with old HdrSrc macros and AAsm, when build with a current tools three classes of difference appear:
* ObjAsm doesn't emit a post increment of 0 for LDR R12,[R12]
* Push/Pull macros use LDR/STR for single words
* WritePSRc adds a safety NOP for ARM2

Version 0.02. Tagged as 'SerialUtils-0_02'