Update unverified parser for nil
Add tests for bytecode interp and fix a bug in division

For integer division: SML div and mod, HOL IntegerTheory.(/) and .(%)
and the bytecode operations are all the same.  These differ from C (and
hardware) / and %, which correspond to SML Int.quot and Int.rem, HOL
IntegerTheory.quot and .rem and are not supported in the bytecode.