Merge remote-tracking branch 'damfr/save-unique-id' into jgrpp

# Conflicts:
#	src/saveload/afterload.cpp
#	src/saveload/saveload.cpp

src/saveload/afterload.cpp

@@ -3597,6 +3597,12 @@ bool AfterLoadGame()
 		}
 	}
 
+	if (SlXvIsFeatureMissing(XSLFI_SAVEGAME_UNIQUE_ID)) {
+		/* Generate a random id for savegames that didn't have one */
+		/* We keep id 0 for old savegames that don't have an id */
+		_settings_game.game_creation.generation_unique_id = _interactive_random.Next(UINT32_MAX-1) + 1; /* Generates between [1;UINT32_MAX] */
+	}
+
 	/* Road stops is 'only' updating some caches */
 	AfterLoadRoadStops();
 	AfterLoadLabelMaps();