Increase MP Command delay to 4 turns, decrease MP turns to 200ms.

To hide network latency, MP turns send commands not for the next turn
but N turns after that (introduced in c684c211a2).
Further, MP turn length was increased to 500ms compared to 200ms SP
turns (introduced in 6a15b78c98).
Unfortunately, increasing MP turn length has negative consequences:
- makes pathfinding/unit motion much worse & unit behaviour worse in
general.
- makes the game more 'lag-spikey', since computations are done less
often, but thus then can take more time.

This diff essentially reverts 6a15b78c98, instead increasing
COMMAND_DELAY from 2 to 4 in MP. This:
- Reduces the 'inherent command lag' in MP from 1000ms to 800ms
- Increases the lag range at which MP will run smoothtly from 500ms to
600ms
- makes SP and MP turns behave identically again, removing the
hindrances described above.

As a side effect, single-player was not actually using COMMAND_DELAY,
this is now done (can be used to simulate MP command lag).

Refs #3752

Differential Revision: https://code.wildfiregames.com/D3275
This was SVN commit r25001.

source/network/NetServer.cpp

@@ -67,6 +67,14 @@ constexpr int FAILED_PASSWORD_TRIES_BEFORE_BAN = 3;
  */
 static const int HOST_SERVICE_TIMEOUT = 50;
 
+/**
+ * Once ping goes above turn length * command delay,
+ * the game will start 'freezing' for other clients while we catch up.
+ * Since commands are sent client -> server -> client, divide by 2.
+ * (duplicated in NetServer.cpp to avoid having to fetch the constants in a header file)
+ */
+constexpr u32 NETWORK_BAD_PING = DEFAULT_TURN_LENGTH * COMMAND_DELAY_MP / 2;
+
 CNetServer* g_NetServer = NULL;
 
 static CStr DebugName(CNetServerSession* session)
@@ -604,7 +612,7 @@ void CNetServerWorker::CheckClientConnections()
 			message = msg;
 		}
 		// Report if the client has bad ping
-		else if (meanRTT > DEFAULT_TURN_LENGTH_MP)
+		else if (meanRTT > NETWORK_BAD_PING)
 		{
 			CClientPerformanceMessage* msg = new CClientPerformanceMessage();
 			CClientPerformanceMessage::S_m_Clients client;