Support UTF-8 encoded Unicode for user communications.

Support UTF-8 encoded Unicode for user communications.
(NF_UTF8, togg): New client flag.
(flash, wall): User text input filtering.
(parse, prmptrd): Normal text input filtering.
(uprmptrd, ugetstring): New, to get user text.
(getele, flash, wall): Use them.
(getele): No need to filter out funny characters; input filtering
takes care of them.
(sendmessage, ufindbreak): Work on user text.
(uprnf): New, to print user text.
(rea, gamedown, show_motd): Use it.
(prnf): Unused, remove.
(pr, upr_player): Normal text output filtering (with highlighting).
(pr_flash): User text output filtering.