- added two more system callbacks for menu customization.

src/d_main.cpp

@@ -3025,6 +3025,9 @@ static void GC_MarkGameRoots()
 	// NextToThink must not be freed while thinkers are ticking.
 	GC::Mark(NextToThink);
 }
+
+bool  CheckSkipGameOptionBlock(const char* str);
+
 //==========================================================================
 //
 // D_DoomMain
@@ -3067,8 +3070,9 @@ static int D_DoomMain_Internal (void)
 		System_GetPlayerName,
 		System_DispatchEvent,
 		StrTable_ValidFilter,
-		StrTable_GetGender
-
+		StrTable_GetGender,
+		nullptr,
+		CheckSkipGameOptionBlock,
 	};