Sets the wormhole entry code in a wormhole status object
General Form: (set-wormhole-entry-code whs code)
See wormhole. Whs should be a well-formed wormhole status and
code should be :ENTER or :SKIP. This function returns a new
status with the specified entry code but the same data as whs. This
function does not affect state or a wormhole's persistent-whs or
ephemeral-whs. It just returns a (possibly) new status object suitable as the
value of the lambda expressions in wormhole-eval and wormhole.