Fixes for spawn farthest DM option

No longer picks a random spot on the first spawn but will account for players spawning in sequentially. No longer fails to return a spawn spot if every player is dead while respawning (instead it picks a random one).

src/g_game.cpp

@@ -1606,10 +1606,20 @@ void FLevelLocals::DeathMatchSpawnPlayer (int playernum)
 	if (selections < 1)
 		I_Error ("No deathmatch starts");
 
+	bool hasSpawned = false;
+	for (int i = 0; i < MAXPLAYERS; ++i)
+	{
+		if (PlayerInGame(i) && Players[i]->mo != nullptr && Players[i]->health > 0)
+		{
+			hasSpawned = true;
+			break;
+		}
+	}
+
 	// At level start, none of the players have mobjs attached to them,
 	// so we always use the random deathmatch spawn. During the game,
 	// though, we use whatever dmflags specifies.
-	if ((dmflags & DF_SPAWN_FARTHEST) && players[playernum].mo)
+	if ((dmflags & DF_SPAWN_FARTHEST) && hasSpawned)
 		spot = SelectFarthestDeathmatchSpot (selections);
 	else
 		spot = SelectRandomDeathmatchSpot (playernum, selections);