Continue work on ODWY440: giant, chalice.

I've introduced the routine original_room_number()
to convert between original room numbers and my own numbers,
since this seems less error-prone than redoing my numbering
scheme (which is mostly inherited from Knuth). This fixes
TODO comments in attempt_hoot() and attempt_fly().

The giant is now almost fully implemented; just some dungeon
stuff remains to implement.

DRINK from the chalice is now implemented.

Minor bugfixes: FILL CHALICE, UP from the chapel, turning
on the lamp should scare the owl away, drinking should cure
thirst, the wording of the "<verb> what?" message.