docs/design/part-events.txt: Update some docs.

Original commit message from CVS:
* docs/design/part-events.txt:
Update some docs.
* docs/design/part-block.txt:
* gst/gstpad.c: (gst_pad_is_blocking), (handle_pad_block),
(gst_pad_push_event):
Revert BLOCKING patch, it tries to be smart without really having a
clear idea what or how. So, now we discard all FLUSHING events again on
a blocking pad. Should fix gnonlin again.
4 files changed