msg: don't allow any escapes in --term-title

Unlike --term-playing-msg, the --term-title string is printed in an
escape sequence already. If we print other escapes during this sequence,
it will abort the sequence and dump the rest of the title string as a
visible string to the user, and possibly beep as well, since the title
string can end with a bel character.

Also updates the manpage to remove a comment about win32, since
terminal-win.c does handle OSC title sequences, calling SetConsoleTitleW.