Reorder the message docs and headers for clarity.

Reorder the message docs and headers for clarity.

Original commit message from CVS:
* docs/gst/gstreamer-sections.txt:
* gst/gstmessage.c: (gst_message_set_buffering_stats),
(gst_message_parse_buffering_stats):
* gst/gstmessage.h:
* gst/gstquery.c: (gst_query_new_latency), (gst_query_set_latency),
(gst_query_parse_latency), (gst_query_new_buffering),
(gst_query_set_buffering_percent),
(gst_query_parse_buffering_percent),
(gst_query_set_buffering_stats), (gst_query_parse_buffering_stats),
(gst_query_set_buffering_avail), (gst_query_parse_buffering_avail):
* gst/gstquery.h:
Reorder the message docs and headers for clarity.
Add aditional buffering stats API for messages.
Add buffering query.
Convert some leftover queries to use GstQuark.
API: gst_message_set_buffering_stats
API: gst_message_parse_buffering_stats
API: GST_QUERY_BUFFERING
API: GstBufferingMode
API: gst_query_new_buffering
API: gst_query_set_buffering_percent
API: gst_query_parse_buffering_percent
API: gst_query_set_buffering_stats
API: gst_query_parse_buffering_stats
API: gst_query_set_buffering_avail
API: gst_query_parse_buffering_avail