removed g_dataset_try_key, g_dataset_force_id and g_dataset_retrive_key in

removed g_dataset_try_key, g_dataset_force_id and g_dataset_retrive_key in

Fri Jun 19 03:11:02 1998  Tim Janik  <timj@gtk.org>

        * gdataset.c: removed g_dataset_try_key, g_dataset_force_id and
        g_dataset_retrive_key in favour of GQuarks.
        a GQuark is an numeric id wich is associated with a certain string.
        (g_quark_try_string): try to get the quark associated with this string,
        if the lookup failed return 0.
        (g_quark_from_string): get the associated quark for a string, if there
        isn't currently a GQuark associated with this string, then allocate a
        new quark and return that.
        (g_quark_from_static_string): like the above function, but the string
        isn't strdup()ed to save memory.
        (g_quark_to_string): get the string that is associated with a certain
        GQuark.

        * gdataset.c (g_dataset_id_set_data_full): invoke the destroy function
        _after_ the new data has been setup.