* Sigh, rewrote set_chanmode() *again* because it was still messy and was doing

  really bad things(tm) with bits in channel modes.  Hopefully I've got it
  right this time.
* Updated supported usermodes on the 004 numeric.
* Updated this.get_usermode() to return the proper usermodes, and whether or
  not we're showing the 'broadcast' modes or not.
* Moved ban stuff out of affect_mode_list() because it's totally different
  than setting + or - o/v.
* CHANLIST_X is now all gone, it was ugly and introduced duplication everywhere
* MODECHAR is gone, too, replaced by MODE[CHANMODE_BIT].modechar
* +/- k/l wasn't working as expected (never -k without args, always allow +l
  with args if different than current limit, and allow -l without args.)
* Fixed a nasty bug courtesy of the old DALnet #square regulars involving the
  bits not being checked right.  Doing +o over and over would just flip the
  bit continuously.