Much of the nickname handling in ircII is ad-hoc and prone to confusion.
Since many people have asked me for a while to fix it, i am writing down
here the plans i have to fix how nicknames are handled.

The current global variable "nickname" will be retained as a global
default.  All new server refnums will use this global default as their
initial nickname.

Each server will maintain three nicknames:

	d_nickname -- This is the "default" for this server.  This is 
		set ONCE, either from the server-spec, or the global 
		nickname, when the server is first connected.  Whenever 
		this server's connection is re-established, this is the 
		nickname that will be used.  It is reset any time the user 
		uses the /NICK command.  It is also reset any time the 
		user's nickname has been established.  This member is
		always set to something after you've first connected to 
		a server.

	s_nickname -- This is the "pending" nickname for the server.
		This is set when the user attempts to change nickname
		through the /NICK command, or when a nick collision
		occurs.  Whenever the user recieves a "Invalid Nickname" 
		or "Nickname is in use", if this member is set, it will 
		be used as the basis for any fudging.  If this member is 
		unset, "nickname" will be used as a starting value.  If 
		this member is set, then a NICK command is still pending.

	nickname -- This is the "official" nickname for the server.
		This is set when we either get a NICK reply back from
		the server for ourselves, or when we recieve the 004
		numeric.  This member must *always* remain correct,
		so that we can determine when the NICK reply comes
		back.  Otherwise, once the current nick is lost, all
		hope is gone.  If this member is set, and s_nickname
		is also set, then that means a NICK command is pending,
		and we are waiting for the reply.

==========================================
What to do when your nickname is rejected
==========================================
Normally, when you do a /nick while connected to the server, and the server
rejects your new nickname, epic will just abandon the change and go back to
your old nickname.

When your nickname is rejected during registration, a new nickname must be
created and submitted to the server.  This process is known as "fudging",
and is only done when you are not connected to a server

----------
Errors while changing nick:

While connected to the server:
   You can do a /NICK
	ACCEPT:		NICK sent to the server
	REJECT:

Error Numerics from NICK command:
	432	Nickname is invalid
	433	Nickname is already in use 
	438	Too many nickname changes (undernet)
	439	Nick changes disallowed (comstud)
	453	Nickname was lost (TS4)

If you're connected, nothing happens
If you're not connected, and /SET AUTO_NEW_NICK is ON, "fudge" the nick
If you're not connected (ie, we're registering), and /SET AUTO_NEW_NICK is OFF,
reset the nick

---------
In change_server_nickname(), called by:
	/NICK command
	462	You Are Already Registered
	fudge_nickname()
	nickname_sendline()
	$serverctl(SET ... NICKNAME ...)
	register_server()
if your new nickname is invalid, and you are connected, reject nick change
if your new nickname is invalid, and you are not connected, reset the nick

-----------
Your nickname is reset (and you are prompted for a new one) when:
	/SET AUTO_NEW_NICK is OFF and NICK fails  while not connected

