AUTH_LOCAL: Setup this connection as authenticated for
FLEXI_SERVER Because all full blown (non-Xnest)
servers can be started only from users logged in
locally, and here GDM assumes only users logged
in from GDM.  They must pass the xauth
MIT-MAGIC-COOKIE-1 that they were passed before
the connection is authenticated.
Note:       The AUTH LOCAL command requires the
--authenticate option, although only
FLEXI XSERVER uses this currently.
Supported since: 2.2.4.0
Arguments:  <xauth cookie>
<xauth cookie> is in hex form with no 0x prefix
Answers:
OK
ERROR <err number> <english error description>
0 = Not implemented
100 = Not authenticated
200 = Too many messages
999 = Unknown error
