Created new file special.h - moved prototypes for special flag

checks there.

Added 'auto-ignore' function, intended for test users.  The new
special flag '+D' will cause a message (FORCE_TESTING) to be
broadcast whenever you log on, to all other logged-on users, making
them ignore you automatically.  Also when a user joins the talker for
the first time after logging on, they will check the 'who' list for
anyone with the flag set, and ignore them.

Test users do ignore each other (but not themselves).
You can unignore a test user at any time, but you will automatically
ignore them again if they log off and on.

I don't recommend setting this flag for test users who log on/off
frequently for the moment, since anyone running an earlier version
will get 'unknown message type #20'.  A possible temporary workaround
might be to broadcast these messages only to people with the 'D' or 'A'
chatprivs, as they are more likely to be running the current cvs
version.  Or to disable broadcasting (the checking when you join the
talker will still work).