Rewrite 3.6.1's compress_str() to avoid peeking past the end of the
input string. This should eliminate the reported valgrind complaint.
The problem was noticed for post-3.6.0 code introduced [by me...] last
June, but it looks like it was present in the old code too.
Also, fix the wording in the paragraph about NUL in the keyhelp text.
tty_putstr() always passes non-message window text through compress_str(),
clobbering usage of two spaces to separate sentences. putstr()'s caller
ought to have more control over that (possibly via its hardly ever used
'attribute' arg?).
Make the whatdoes ('&' or '?f') command support the 'altmeta' option
for meta-characters generated by two character seqeunce 'ESC char'.
Also, make it be more descriptive when reporting "no such command"
by including the numeric value it operated on when failing to match
any command. That might provide a way for us to get some extra
information when players report problems with odd keystrokes: we ask
them to type such at the "what command?" prompt and then tell us what
numbers come up.
It's been given a help file to deal with assorted idiosyncracies
which can come up when querying what keys do. Unfortunately that
ended up being way more verbose than intended.
Installation of the extra data file has only been done for Unix.
Other platforms will get "can't open file" if they respond with
'&' or '?' to the "what command?" prompt. The command will still
work though, just without the extra text.
