docs/design/: Some more docs in the works.

docs/design/: Some more docs in the works.

Original commit message from CVS:
* docs/design/part-dynamic.txt:
* docs/design/part-events.txt:
* docs/design/part-seeking.txt:
Some more docs in the works.

* gst/base/gstbasetransform.c: (gst_base_transform_transform_caps),
(gst_base_transform_getcaps), (gst_base_transform_configure_caps),
(gst_base_transform_setcaps), (gst_base_transform_get_size),
(gst_base_transform_buffer_alloc), (gst_base_transform_event),
(gst_base_transform_handle_buffer),
(gst_base_transform_sink_activate_push),
(gst_base_transform_src_activate_pull),
(gst_base_transform_set_passthrough),
(gst_base_transform_is_passthrough):
Refcounting fixes.

* gst/gstbus.c: (gst_bus_source_dispatch), (gst_bus_poll):
Cleanups.

* gst/gstevent.c: (gst_event_finalize):
Set SRC to NULL.

* gst/gstutils.c: (gst_element_unlink),
(gst_pad_get_parent_element), (gst_pad_proxy_getcaps),
(gst_pad_proxy_setcaps):
* gst/gstutils.h:
Add _get_parent_element() to get a pads parent as an element.