docs/: Correct fixxrefs options.

docs/: Correct fixxrefs options.

Original commit message from CVS:
* docs/gst/Makefile.am:
* docs/libs/Makefile.am:
Correct fixxrefs options.
* docs/plugins/Makefile.am:
* docs/plugins/gstreamer-plugins-docs.sgml:
* docs/plugins/gstreamer-plugins-sections.txt:
* plugins/elements/Makefile.am:
* plugins/elements/gstcapsfilter.c (gst_capsfilter_details):
* plugins/elements/gstcapsfilter.h (__GST_CAPSFILTER_H__,
GST_TYPE_CAPSFILTER, GST_CAPSFILTER, GST_CAPSFILTER_CLASS,
GST_IS_CAPSFILTER, GST_IS_CAPSFILTER_CLASS, GstCapsFilter,
GstCapsFilterClass, _GstCapsFilter, trans, filter_caps,
_GstCapsFilterClass, trans_class):
* plugins/elements/gstelements.c (name, rank, type, _elements):
* plugins/elements/gstidentity.c
(gst_identity_check_imperfect_timestamp,
gst_identity_check_imperfect_offset):
Document capsfilter and add doc-blurb to identity.