gst/playback/gstdecodebin.c: Implement delayed caps linking needed for element with a lot of different caps on the sr...

Original commit message from CVS:
* gst/playback/gstdecodebin.c: (dynamic_create), (dynamic_free),
(close_pad_link), (dynamic_remove), (no_more_pads), (new_caps),
(find_dynamic), (unlinked), (close_link):
Implement delayed caps linking needed for element with a lot of
different caps on the src pads that get fixed at runtime.
Improve management of dynamic elements.
* gst/playback/gstplaybasebin.c: (gst_play_base_bin_init),
(group_destroy), (group_commit), (check_queue), (queue_overrun),
(gen_preroll_element), (remove_groups), (unknown_type),
(add_element_stream), (no_more_pads_full), (no_more_pads),
(sub_no_more_pads), (source_no_more_pads), (preroll_unlinked),
(new_decoded_pad), (setup_subtitle), (array_has_value),
(gen_source_element), (source_new_pad), (has_all_raw_caps),
(analyse_source), (remove_decoders), (make_decoder),
(remove_source), (setup_source), (finish_source), (prepare_output),
(gst_play_base_bin_change_state):
* gst/playback/gstplaybasebin.h:
Use more _CAST instead of full type checking casts.
Small cleanups, plug some leaks.
Handle dynamic sources.
Add some helper functions to create lists of strings used for
blacklisting and other stuff.
Refactor some code dealing with analysing the source.
Re-enable sources without pads (like cd:// or other selfcontained
elements).