Replays: keep party in sync with current viewpoints

- More and more parts of the game rely on parties
- Parties are assumed to match the displayplayers
- This fixes A/B/C/D nametags

src/g_demo.c

@@ -40,6 +40,7 @@
 #include "lua_hook.h"
 #include "md5.h" // demo checksums
 #include "p_saveg.h" // savebuffer_t
+#include "g_party.h"
 
 // SRB2Kart
 #include "d_netfil.h" // nameonly

src/m_menu.c

@@ -6208,12 +6208,10 @@ static void M_PlaybackAdvance(INT32 choice)
 	paused = true;
 }
 
-
 static void M_PlaybackSetViews(INT32 choice)
 {
-
 	if (demo.freecam)
-		return;	// not here.
+		return; // not here.
 
 	if (choice > 0)
 	{
@@ -6222,8 +6220,14 @@ static void M_PlaybackSetViews(INT32 choice)
 	}
 	else if (r_splitscreen)
 	{
-		r_splitscreen--;
-		R_ExecuteSetViewSize();
+		if (choice == 0)
+		{
+			G_SyncDemoParty(displayplayers[r_splitscreen], r_splitscreen - 1);
+		}
+		else
+		{
+			G_SyncDemoParty(consoleplayer, 0);
+		}
 	}
 }