Use trapname() in several more places. I wasn't systematic about it.
trapname() could generate a random value of 0 and attempt to use
"real trap #0" but 0 is NO_TRAP. So it ended up with "water" from
the preceding block of entries in defsyms[]. Treat 0 as an extra
chance for the actual trap instead of an hallucinatory one.
Add a couple more hallucinatory traps. "Roach Motel" is trademarked
but like Spam and Band-Aid, general usage has trampled over it. I
included "(tm)" anyway. Also, sometimes generate "<role> trap" or
"<rank> trap" on the fly. Why should tourists get all the fun?