Add a new last-buffer property that contains the last buffer used in basesink for...

Add a new last-buffer property that contains the last buffer used in basesink for preroll or rendering. useful for ma...

Original commit message from CVS:
* docs/libs/gstreamer-libs-sections.txt:
* libs/gst/base/gstbasesink.c: (gst_base_sink_class_init),
(gst_base_sink_get_last_buffer), (gst_base_sink_set_last_buffer),
(gst_base_sink_get_property), (gst_base_sink_render_object),
(gst_base_sink_preroll_object),
(gst_base_sink_queue_object_unlocked), (gst_base_sink_event),
(gst_base_sink_change_state):
* libs/gst/base/gstbasesink.h:
Add a new last-buffer property that contains the last buffer used in
basesink for preroll or rendering. useful for making snapshots.
API: gst_base_sink_get_last_buffer()
API: GstBaseSink::last-buffer