The JIT and bytecode compiler disagreed on the definition of
"constant". Now there are two levels: "constant" means constant across
all instantiations, and "fixed" means constant for a given instantation.
The JIT uses this distinction to generate direct-primitive calls
or not. (Without the distinction, a direct jump to `reverse' could
be wrong, because `racket/base' might get instantiated with the
JIT disabled or not.)
Also, fixed a bug in the JIT's `vector-set!' code in the case that
the target vector is a top-/module-level reference that is ready,
fixed, or constant.
7eb2042bd9