docs/design/part-negotiation.txt: Update with, um, one way that pull-mode negotiation...

docs/design/part-negotiation.txt: Update with, um, one way that pull-mode negotiation might work?

Original commit message from CVS:
2007-01-10  Andy Wingo  <wingo@pobox.com>

* docs/design/part-negotiation.txt: Update with, um, one way that
pull-mode negotiation might work?

* gst/gstpad.h:
* gst/gstpad.c (gst_pad_get_allowed_caps): Remove the restriction
that the pad must be a src pad; makes sense to call it the other
way in pull mode, and the logic is symmetric anyway.