gst/playback/: More fixes on reusing of the element.

gst/playback/: More fixes on reusing of the element.

Original commit message from CVS:
* gst/playback/gstdecodebin.c: (gst_decode_bin_get_type),
(gst_decode_bin_class_init), (gst_decode_bin_factory_filter),
(compare_ranks), (print_feature), (gst_decode_bin_init),
(gst_decode_bin_dispose), (find_compatibles), (close_pad_link),
(try_to_link_1), (new_pad), (close_link), (type_found),
(gst_decode_bin_set_property), (gst_decode_bin_get_property),
(gst_decode_bin_change_state), (plugin_init):
* gst/playback/gstplaybasebin.c: (gst_play_base_bin_get_type),
(gst_play_base_bin_class_init), (gst_play_base_bin_init),
(gst_play_base_bin_dispose), (queue_overrun),
(gen_preroll_element), (remove_prerolls), (no_more_pads),
(new_stream), (setup_source), (gst_play_base_bin_set_property),
(gst_play_base_bin_get_property), (play_base_eos),
(gst_play_base_bin_change_state), (gst_play_base_bin_add_element),
(gst_play_base_bin_remove_element),
(gst_play_base_bin_mute_stream), (gst_play_base_bin_link_stream),
(gst_play_base_bin_unlink_stream),
(gst_play_base_bin_get_streaminfo):
* gst/playback/gstplaybasebin.h:
* gst/playback/gstplaybin.c: (gst_play_bin_get_type),
(gst_play_bin_class_init), (gst_play_bin_init),
(gst_play_bin_dispose), (gst_play_bin_set_property),
(gst_play_bin_get_property), (gen_video_element),
(gen_audio_element), (remove_sinks), (setup_sinks),
(gst_play_bin_change_state), (gst_play_bin_get_event_masks),
(gst_play_bin_send_event), (gst_play_bin_get_formats),
(gst_play_bin_convert), (gst_play_bin_get_query_types),
(gst_play_bin_query), (plugin_init):
* gst/playback/test4.c: (main):
More fixes on reusing of the element.