gst/gststructure.c: Convert function to use gst_value_serialize().

gst/gststructure.c: Convert function to use gst_value_serialize().

Original commit message from CVS:
* gst/gststructure.c: (gst_structure_to_string):
Convert function to use gst_value_serialize().
* gst/gstvalue.c: (gst_value_serialize_list),
(gst_value_serialize_fourcc), (gst_value_serialize_int_range),
(gst_value_serialize_double_range), (gst_value_serialize_boolean),
(gst_value_serialize_int), (gst_value_serialize_double),
(gst_string_wrap), (gst_value_serialize_string),
(gst_value_serialize), (gst_value_deserialize):
* gst/gstvalue.h:
Add implementations for serialize.