make compiled code raise Div if about to div by 0, and always re-raise Bind/Div

also add a small test of this behavior.

the code is instrumented on translation into the intermediate language
(rather than into bytecode) so it will be subject to future
simplification phases.
start updating intlang for new div/mod semantics

the intlang semantics now (like the bytecode) requires div/mod to be
applied to a non-zero argument (or evaluation gets stuck).