A known issue with gdmdynamic is that when a display connects to
        the server it generates the gdmdynamic "ADD" and "RELEASE" commands.
        On startup, hundreds of displays could send these commands at once
        and cause the server too be flooded with sockets requests.  Hammering
        the socket like this caused me to find and fix a number of problems
        that improve socket reliability for general GDM use.  I also enhanced
        gdmdynamic so it is more sensitive to the socket being busy and no
        longer overloads it, instead sleeping and retrying if necessary.  This
        allows gdmdynamic to work if there are hundreds of displays instead of
        just a dozen or so.

        * daemon/gdm.[ch]: Added new "SERVER_BUSY" sockets command so that
          gdmdynamic can sleep before starting new slaves if the daemon is
          already busy.
        * daemon/gdm-net.[ch]: Bump up MAX_CONNECTIONS from 10 to 15.  I notice
          that this improves performance significantly when hammering the
          daemon with connections.  Added better comments for this logic and
          now debug logs when a subconnection is thrown away.  New
          gdm_connection_is_server_busy function
        * daemon/display.c: Correct DYNAMIC_REMOVE so it works and fixes bug
          #326796.  Before it wasn't really removing the displays.
        * gui/gdmdynamic.c: Quite a bit of work to make gdmdynamic avoid
          flooding the server with sockets requests.  Now it sets sockets
          retries to 1 and manages sleeping and retries itself.
        * gui/gdmconfig.c: Added gdm_config_set_comm_retries so that slaves can
          specify how many retries they want the comm logic to use.
        * gui/gdmcomm.c: Now do_command returns NULL when it gets back "",
          which happens when a subconnection was dropped by the daemon.  This
          lets the slave try the connection again.   Now error messages are
          always logged, not just when debug is turned on.  Added
          gdmcomm_did_connection_fail and gdmcomm_set_allow_sleep so
          gdmdynamic can control the behavior of how the connection works.
        * gui/gdmcommon.c, gui/gdmchooser.c, gui/gdmlogin.c, gui/greeter/greeter.c:
          Fix gdm_common_fail so it doesn't generate compile errors when building
          with GCC.  Fixes bug #330480.
        * docs/C/gdm.xml: Cleaned up section that explains sockets commands so
          that they are in alphabetical order, added info about SERVER_BUSY
          and new gdmdynamic -s and -t options.
        * config/gdm.conf: Better description of how debug works, perhaps
          I just didn't like the word "spew".
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