check/gst/gstghostpad.c: Added some more tests for wrong hierarchy

check/gst/gstghostpad.c: Added some more tests for wrong hierarchy

Original commit message from CVS:
* check/gst/gstghostpad.c: (GST_START_TEST), (gst_ghost_pad_suite):
Added some more tests for wrong hierarchy

* docs/design/part-overview.txt:
Some updates.

* gst/gstbin.c: (gst_bin_remove_func), (gst_bin_dispose):
Cleanups.

* gst/gstelement.c: (gst_element_remove_pad), (gst_element_seek),
(gst_element_dispose):
Some more cleanups.

* gst/gstpad.c: (gst_pad_link_check_compatible_unlocked),
(gst_pad_link_check_hierarchy), (gst_pad_link_prepare),
(gst_pad_get_caps_unlocked), (gst_pad_accept_caps),
(gst_pad_set_caps), (gst_pad_send_event):
Check for correct hierarchy when linking pads. Moving to
strict requirement for ghostpads when linking elements in
different bins.

* gst/gstpad.h:
Clean ups. Added WRONG_HIERARCHY return value.