* module/language/tree-il/compile-cps2.scm (convert): Fix bug
in (apply - ...), because the instruction for "-" is "sub", and
"sub" lookup was failing. Caught by numbers.test. Really I would
like to get rid of $prim, somehow.
* module/language/tree-il/compile-cps2.scm (adapt-arity): New
procedure. This is equivalent to (language cps arities), but as it
is a necessary pass and not an optimization it's more proper to put
it in the converter itself. Unlike with the nested CPS
representation, it's possible to look up continuations without
making a DFG.
(convert): Adapt arities as necessary.
