added two new functions to the docs documents all undocumented GstXXXFlags completed some incomplete docs

Original commit message from CVS:
* docs/gst/gstreamer-sections.txt:
* gst/base/gstbasesrc.h:
* gst/gstelement.h:
* gst/gstevent.h:
* gst/gstobject.h:
* gst/gstpad.h:
* gst/gstpipeline.c:
* gst/gstpipeline.h:
* gst/gstutils.h:
* gst/gstxml.h:
added two new functions to the docs
documents all undocumented GstXXXFlags
completed some incomplete docs