Add a consistent two blank lines at game end, for Parchment.
Add a map of the twisty maze (all alike).

I know there's a map of this maze somewhere on the Internet,
but I can never find it when I'm looking for it. So I just put
one together myself.

I believe this is a complete map. Up and down connections are
indicated by stairsteps in the logical directions. Each dead-end
room has an additional connection via the motion word "OUT".
There's also a CLIMB/DOWN connection from 57 (Brink of Pit),
of course, but I didn't have room to show it.

The large room numbers match Woods' code (WOOD0350/advent.dat).
The small slanted identifiers are Knuth's (KNUT0350/advent.w).
Fix another FEED BEAR bug.

Turns out feeding the bear while it's still live and ferocious
would also give a bad response: in this case, no response at all.
I introduced this bug in my initial port of Knuth's code.
Fix the message in the maze.

Knuth quietly changed the word "leaves" to "hides" in his version.
I'm changing it back.
Fix the message for "THROW [foo]" when not carrying it.

Knuth's version gets this wrong, by setting an incorrect string value
for default_msg[TOSS].
Fix the response to "FIND GULLY".

I'm somewhat disappointed that neither GCC nor Clang warned me
about this bug. FIND and INVENTORY are not MotionWords, but
ActionWords. Knuth's code gets this right; I introduced the bug
during my original port. The gist of Woods' code is that if the
player uses a motion word but *also* uses the word FIND (or
INVENTORY, for some reason), then we give the "I cannot tell you
where remote things are" message in preference to the "I don't
know how to apply that word here" message.

Due to what was probably sloppiness in Woods' original version,
the commands FIND CRAWL, FIND XYZZY, and FIND PLUGH do *not*
give the "I cannot tell you..." message when they fail.

Also, notice that FIND GULLY will act the same as GULLY by
itself, if the motion word GULLY is in fact an exit from the
current room. The new codepath is executed only if "mot" wasn't
found in the travel table for the current room.
Get rid of the first[] and visits[] arrays.

The (poorly-named) first[] array is now known as places[].objects;
each place now keeps track of the list of objects present there.

I had apparently been in the process of refactoring away the visits[]
array already, since places[].visits already existed but was unused.
Removing that redundancy saves some space on the Z-machine.
Remove the verb ABSTAIN, and set NOTHING to 0 instead of 200.

In Knuth's original port, ABSTAIN was the ActionWord with value 0
and NOTHING was the ObjectWord with value 0. Now that all "real"
words have values greater than 100, it doesn't make much sense to
have two different "no-input" words. So, I've put NOTHING back to 0
(making it WordClass_None) and removed ABSTAIN completely.

Notice that the conditional movement instructions (only_if_toting,
only_if_here, unless_prop) won't work correctly with an argument
of MIN_OBJ. That's not a problem as long as MIN_OBJ is KEYS, since
no conditional instruction in this game is triggered by the keys.
Merge branch 'master'

This fixes a number of non-original bugs:

  - FEED BEAR without food while bear is hostile (fb5dd8c1)
  - Wording of message in the maze (dfdc60a9)
  - Wrong message for THROW X while not carrying X (0ffadde2)
  - Wrong message for FIND GULLY (05721154)