Remove XnestDisplayArg configuration choice. In discussion with Alan
    
    2006-03-13  Brian Cameron  <brian.cameron@sun.com>
    
            * configure.ac, daemon/server.c, daemon/gdmconfig.c,
              config/gdm.conf.in, config/Makefile.am: Remove
              XnestDisplayArg configuration choice.  In discussion with
              Alan Coopersmith <Alan.Coopersmith@sun.com> from the Xserver
              team it should be fine to avoid using -display when calling
              Xnest/Xephyr all the time and just use the DISPLAY environment
              variable.  Better to not add a configuration choice if it is
              not needed.
    
    svn path=/trunk/; revision=4677