FLEXI_XNEXT: Start a new flexible Xnest server
Note:        Supported an older version from 2.2.4.0, later
2.2.4.2, but since 2.3.90.4 you must supply 4
arguments or ERROR 100 will be returned.  This
will start Xnest using the XAUTHORITY file
supplied and as the uid same as the owner of
that file (and same as you supply).  You must
also supply the cookie as the third argument
for this display, to prove that you indeed are
this user.  Also this file must be readable
ONLY by this user, that is have a mode of 0600.
If this all is not met, ERROR 100 is returned.
Note:        The cookie should be the MIT-MAGIC-COOKIE-1,
the first one GDM can find in the XAUTHORITY
file for this display.  If that's not what you
use you should generate one first.  The cookie
should be in hex form.
Supported since: 2.3.90.4
Arguments:  <display to run on> <uid of requesting user>
<xauth cookie for the display> <xauth file>
Answers:
OK <display>
ERROR <err number> <english error description>
0 = Not implemented
1 = No more flexi servers
2 = Startup errors
3 = X failed
4 = X too busy
5 = Xnest can't connect
6 = No server binary
100 = Not authenticated
200 = Too many messages
999 = Unknown error
