Changes in V2.40:

  * Quetzal save file support.

  * Use the `-R' command line option to enable save/restore of old Frotz
    format save files.

  * More memory-efficient undo scheme based on the method used in
    Evin Robertson's Nitfol interpreter.

  * If the ZCODE_PATH environment variable is defined, search it for
    game, graphics and sound files.  If ZCODE_PATH is not defined, try
    INFOCOM_PATH.

  * Added "ZSTRICT" error checking.

  * err.c: New source file to handle runtime_error () and the
    additional ZSTRICT errors consistently.

  * sound.c:z_sound_effect: Assume sound number 0 refers to current sound.
    screen.c:z_set_cursor: 
        if (y == 0)		/* use cursor line if y-coordinate is 0 */
	    y = wp[win].y_cursor;
        if (x == 0)		/* use cursor row if x-coordinate is 0 */
	    x = wp[win].x_cursor;
    Fixes incorrect cursor positioning in some games (e.g. the
    help screen in dumont.z5).