lobby

21. Added Support for the "map00 lobby convention" in WADs. It's
    controlled via the "lobby" CVAR. When that CVAR is 1, it activates
    the "lobby mode":
       1. The server auto-switches to map00 when both players leave.
       2. The server auto-switches to map00 when a map ends.
       3. All maps will always be available for voting, no matter
          the value of sv_vote_map_skip.
       4. There will be no time limit on map00.
       5. Dynamic bots (minplayers) are excluded from map00.

    For this mode to get activated, you need to:
       a. Set the "lobby" CVAR to a value of 1.
       b. map00 should exist in the loaded WADs.
       c. Define a maplist on the server.
       d. Include map00 into the maplist.