New `#%app/no-return` and `#%app/value` functions at the Chez Scheme
level allow schemify to communicate that function calls will not
return or will return a single value. The schmeify pass may have this
information because a Racket-level primitive is declared that way
(such as `error` or `raise-argument-error` for no-return, or most
functions for single-valued) or because single-valuedness is inferred.
There's currently no inference for no-return functions, because those
are relatively rare. An `#%app/value` is used by schemify only for
imported, non-inlined functions, since cp0 can already deal with local
functions and primitives.
There's a start here at adapting the "optimize.rktl" test suite for CS
--- and that effort triggered these improvements plus some other
low-hanging fruit. But a lot more is needed to adapt "optimize.rktl"
and to make some additional optimizations happen.
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