peekbot update

I added some new decoders to peekbot

Also, the symbols table used by the disassembler has been extended to allow for decoding of functions that are all called via a single address (e.g. the BBC has a routine called OSBYTE which is accessed via $FFF4, but has hundreds of different sub-functions which can be selected via different values of A,X & Y registers). Only immediate loads in the vicinity of the JSR are interepreted (e.g. LDA #$01/ JSR $FFF4).