configure.ac: Add detection for HAVE_PRINTF_EXTENSION and

configure.ac: Add detection for HAVE_PRINTF_EXTENSION and

Original commit message from CVS:
* configure.ac: Add detection for HAVE_PRINTF_EXTENSION and
GST_PRINTF_EXTENSION_FORMAT_DEFINE.
* docs/random/ds/0.9-suggested-changes: Notes from Company.
* gst/gstcaps.c: (gst_caps_to_string): Add comment.
* gst/gstconfig.h.in: Add define for GST_PTR_FORMAT
* gst/gstinfo.c: (_gst_debug_init), (gst_debug_print_object),
(gst_debug_log_default), (_gst_info_printf_extension),
(_gst_info_printf_extension_arginfo):  Add printf extension.
* gst/gstinfo.h: remove G_GNUC_PRINTF, because it doesn't work with %P
* gst/gststructure.c: (gst_structure_to_string),
(_gst_structure_parse_value): Use gst_value_deserialize() and
remove old code.
* gst/gstvalue.c: (gst_value_deserialize_fourcc),
(gst_value_deserialize_boolean), (gst_strtoi),
(gst_value_deserialize_int), (gst_value_deserialize_double),
(gst_value_deserialize_string), (gst_value_deserialize): Implement
a bunch of deserialize functions and gst_value_deserialize.
* gst/gstvalue.h: er, _de_serialize, not unserialize
* testsuite/caps/string-conversions.c: (main): We don't currently
handle (float) in caps, so convert these to (double).
* testsuite/debug/Makefile.am: Add new test for the printf extension
* testsuite/debug/printf_extension.c: (main): same