Add initial support for loading JokerPP savegames

See #123

src/saveload/tracerestrict_sl.cpp

@@ -65,6 +65,15 @@ static void Load_TRRP()
 		SlObject(&stub, _trace_restrict_program_stub_desc);
 		prog->items.resize(stub.length);
 		SlArray(&(prog->items[0]), stub.length, SLE_UINT32);
+		if (SlXvIsFeaturePresent(XSLFI_JOKERPP)) {
+			for (size_t i = 0; i < prog->items.size(); i++) {
+				TraceRestrictItem &item = prog->items[i]; // note this is a reference,
+				if (GetTraceRestrictType(item) == 19 || GetTraceRestrictType(item) == 20) {
+					SetTraceRestrictType(item, (TraceRestrictItemType)(GetTraceRestrictType(item) + 2));
+				}
+				if (IsTraceRestrictDoubleItem(item)) i++;
+			}
+		}
 		CommandCost validation_result = prog->Validate();
 		if (validation_result.Failed()) {
 			char str[4096];