Add the FM hardware checker tool (ONGCHK.COM) from the PMD driver

This executable is embedded into all 4 versions of ZUN.COM. It was written by
KAJA, not ZUN, so we don't care about anything in there - not that it would
matter for porting anyway. We only need that binary to be able to create
bit-perfect rebuilds of ZUN.COM in the future.
Update the Readme file to match the recent ZUN.COM developments

No point in having lame excuses for not dumping it when we've actually started
doing so.