#231 configure show/hide channel status messages

[bzb]

Need feature to allow user of xchat to configure whether to show channel user status messages such as:

abc is now known as ...
abc has quit ...
abc has left ...
abc has joined ...
etc

Correspondingly, the user status should be highlighted in the user list.
example:
when a user has joined, use normal black color
when a user has quit, remove user from userlist.
when a user is away, gray user entry
when a user has changed nicks, highlight to orange ...until xchat user clicks on the nick to reset to black
etc

Alternatively, decide to use a character symbols before the user nick to indicated the condition.
example:
when a user is away, use '_'
when a user has changed nicks, use '*'