gst/playback/: Make playbin async, it'll commit state to paused when all streams...

gst/playback/: Make playbin async, it'll commit state to paused when all streams are detected.

Original commit message from CVS:
* gst/playback/Makefile.am:
* gst/playback/gstdecodebin.c: (gst_decode_bin_init),
(gst_decode_bin_dispose), (dynamic_create), (dynamic_free),
(free_dynamics), (pad_unblocked), (pad_blocked), (close_pad_link),
(try_to_link_1), (new_pad), (no_more_pads), (type_found),
(gst_decode_bin_change_state):
* gst/playback/gstplaybin.c: (gst_play_bin_class_init),
(gst_play_bin_send_event_to_sink):
* gst/playback/test5.c: (new_pad), (no_more_pads), (start_finding),
(dump_element_stats), (main):
* gst/playback/test6.c: (main):
Make playbin async, it'll commit state to paused when all streams
are detected.
Remove ugly hack.
Added test6.c to show async behaviour.