Add misc/checkout-latest-good-commit script which iterates over previous commits to find the latest which allows a command to run successfully
Undo forced use of ___alloc_scmobj by ##bignum.make
Introduce ___SIZE_TS to mimick uses of "long" type prior to commit c89610066937d51eeeac866bb6320bcd5bd61f87 which had introduced a memory management bug (this will need further investigation to determine where in the code the sign is important)