Remove script which is no longer used
lib/,src/cavern.h,src/commands.c,tests/badbegin.out: Improve cavern
messages which talk about "tags" and/or "prefixes" in *begin and *end
commands to instead talk about "survey names".
lib/merge-po: If a msgid has changed, use the old msgstr for that
msgno and automatically mark it as fuzzy.
src/cad3d.c: Whitespace tweak.