gst/gstbuffer.h: Documentation fix.

gst/gstbuffer.h: Documentation fix.

Original commit message from CVS:
* gst/gstbuffer.h:
Documentation fix.

* gst/gstpad.c: (gst_pad_init), (gst_pad_acceptcaps_default),
(gst_pad_accept_caps), (gst_pad_configure_sink),
(gst_pad_configure_src), (gst_pad_chain), (gst_pad_push):
Make the default acceptcaps behaviour be to check the requested
caps against the gst_pad_get_caps output.

Ensure that gst_pad_accept_caps is used to check caps when a pad
doesn't have a setcaps function, so that pads automatically refuse
caps that they don't allow in their pad template. (Fixes #332986)

When a buffer with attached caps is pushed, ensure that the source
pad receives those caps even if the element didn't call
gst_pad_set_caps first.