Bump version number, we're now 0.9.0

Bump version number, we're now 0.9.0

Original commit message from CVS:
* configure.ac:
* gst/gst_private.h:
* gst/gstbin.c: (gst_bin_add_func), (gst_bin_add),
(gst_bin_remove_func), (gst_bin_remove),
(gst_bin_get_by_name_recurse_up):
* gst/gstclock.c: (gst_clock_id_ref), (gst_clock_id_unref),
(gst_clock_id_compare_func), (gst_clock_id_wait),
(gst_clock_id_wait_async), (gst_clock_init),
(gst_clock_adjust_unlocked), (gst_clock_get_time):
* gst/gstelement.h:
* gst/gstinfo.c: (_gst_debug_init):
* gst/gstobject.h:
* gst/gstpad.c: (_gst_pad_default_fixate_foreach),
(gst_pad_collectv), (gst_pad_collect_valist), (gst_pad_query):
* gst/gstpad.h:
Bump version number, we're now 0.9.0
Add future debugging category.
Fix NULL _unref() in _get_by_name_recurse_up
Rearrange gstpad.h.
Update some docs.