Synopsis:
   $ischannel(<channel name>)

Technical:
   This function checks whether the input channel name is a valid channel
   name.  It does NOT check whether the channel actually exists, only that
   the name would be legal to use as a channel name.

Practical:
   This function compares the given channel name against the known server
   rules for channel names to determine if the server is likely to allow
   a channel with such a name.  Contrary to common belief, it does not
   check for the existence of a channel.

Returns:
   "true" value if channel name is legal, "false" otherwise

Examples:
   $ischannel(#blah)              returns true
   $ischannel(&blah)              returns true
   $ischannel(blah)               returns false

See Also:
   join(1)

Bugs:
   This function does not take ircd 2.9's modeless channels (prefixed with
   a '+') into account when determining the legality of a channel name.