Remove trailing whitespace from all files.

Satisfy the default git commit hook, which forbids trailing whitespace
and files ending with anything other than a single newline.
No functional change.
Add "POTTERY" as a synonym for "VASE".

I accidentally omitted this synonym in my transcription
of Knuth's code; Knuth had it right.
Remove "SLAY" as a synonym for "KILL" in Adv350.

It's unclear what the history is here. "SLAY" does not appear
in my copy of WOOD0350, nor in LUPI0440, but it does appear
independently in WOOD0430 and MCDO0551. It also appears in
KNUT0350 (perhaps imported from WOOD0430, since Woods collaborated
with Knuth on that version) and PLAT0550 (maybe independent,
or maybe cross-pollinated by Mike Arnautov).
Remove the flag bits for F_LIGHTED and F_WATER.

It seems simpler to just use helper functions has_light() and has_water()
for these features (and add a helper has_oil() for R_EPIT), rather than
trying to maintain Knuth's flag bits.

No functional change.
Start work on Luckett & Pike's ADV440.