ADD_DYNAMIC_DISPLAY: Create a new server definition that will run on the
specified display leaving, it in DISPLAY_CONFIG state.
Supported since: 2.8.0.0
Arguments:  <display to run on>=<server>
Where <server> is either a configuration named in gdm.conf or
a literal command name.
Answers:
OK <display>
ERROR <err number> <english error description>
0 = Not implemented
2 = Existing display
3 = No server string
4 = Display startup failure
100 = Not authenticated
200 = Dynamic Displays not allowed
999 = Unknown error
