- In conjunction with all the below changes, attempt to fix A_CheckSightOrRange and A_CheckSight

for multiplayer: They now always check through the eyes of every player. For players whose
  cameras are not players, they also check through the eyes of those cameras.
- Using spynext/spyprev to switch from a non-player to a player now writes a command to the
  network stream and lets Net_DoCommand() take care of it later. The logic here is that if
  a player is viewing from something that isn't another player, then every player needs to know
  about it for sync purposes. Consequently, when they stop viewing from a non-player and switch
  to a player, everybody needs to know about that too. But if they are viewing from a
  player, it doesn't matter which player it is, so they can spynext/spyprev all they want
  without letting the other players know about it (and without potentially breaking demos--due
  to the above-mentioned two codepointers--while doing it during demo playback).
- Replaced the instances of checking players[consoleplayer].camera for a valid pointer to
  ones that do it for every player.
- Fixed: Upon changing levels, all players but the consoleplayer would have their cameras NULLed.
- Fixed: player_t::FixPointers() needs to bypass the read barriers, or it won't be able to
  do substitutions of old objects that are pending deletion.

SVN r3448 (trunk)

src/d_net.cpp

@@ -592,13 +592,16 @@ void PlayerIsGone (int netnode, int netconsole)
 		Printf ("%s left the game\n", players[netconsole].userinfo.netname);
 	}
 
-	// [RH] Revert to your own view if spying through the player who left
-	if (players[consoleplayer].camera == players[netconsole].mo)
+	// [RH] Revert each player to their own view if spying through the player who left
+	for (int ii = 0; ii < MAXPLAYERS; ++ii)
 	{
-		players[consoleplayer].camera = players[consoleplayer].mo;
-		if (StatusBar != NULL)
+		if (playeringame[ii] && players[ii].camera == players[netconsole].mo)
 		{
-			StatusBar->AttachToPlayer (&players[consoleplayer]);
+			players[ii].camera = players[ii].mo;
+			if (ii == consoleplayer && StatusBar != NULL)
+			{
+				StatusBar->AttachToPlayer (&players[ii]);
+			}
 		}
 	}
 
@@ -2460,6 +2463,10 @@ void Net_DoCommand (int type, BYTE **stream, int player)
 		F_AdvanceIntermission();
 		break;
 
+	case DEM_REVERTCAMERA:
+		players[player].camera = players[player].mo;
+		break;
+
 	default:
 		I_Error ("Unknown net command: %d", type);
 		break;