Restore death scarabs' corpses.

Mea culpa: they were added intentionally, but that should have been
in a separate commit.
Simplify.
Use an enum (PleasingFungus).
Remove MISC_MISCAST.

The cost of an enum entry is low, the cost of programmer confusion
is somewhat higher. Also allows cleaning up code slightly.
Change the mummy death curse message.

Instead of "an indirect mummy death curse", "a guardian mummy's death
curse" or "Khufu's death curse."
Fix feature overrides if a magic mapped symbol is not specified (#9177).

Not sure why this ever worked.
Simplify.