This summarizes the changes I have made to implement more complete availability of particle genealogy information in BBSIM's XDR output. Will commit when SLAC networking is working.

I am now looking at how best to access the STDHEP common on the C++ side. Surprisingly enough this seems to be new territory; noone's done it yet (if you know different, let me know).

STDHEP common written to a block in XDR file header
Available on C++ side as just the common block at present; nothing done on accessing it
geant3.ds mod for gTrack structure: hepid element added to record HEPEVT parent of track from KINE bank user word
TrksToDs.F modified to load hepid from user word
No backward compatibility of XDR files between next SRT release and previous, unless special action taken. bbdata.ds version ID bumped.