libs/gst/: Documentation updates.

libs/gst/: Documentation updates.

Original commit message from CVS:
* libs/gst/base/gstadapter.c:
* libs/gst/base/gstadapter.h:
* libs/gst/base/gstbasesink.c: (gst_base_sink_class_init),
(gst_base_sink_get_position):
* libs/gst/base/gstbasesink.h:
* libs/gst/base/gstbasesrc.c: (gst_base_src_class_init),
(gst_base_src_default_query), (gst_base_src_default_do_seek),
(gst_base_src_do_seek), (gst_base_src_perform_seek),
(gst_base_src_send_event), (gst_base_src_update_length),
(gst_base_src_get_range), (gst_base_src_loop),
(gst_base_src_start):
* libs/gst/base/gstbasesrc.h:
* libs/gst/base/gstbasetransform.h:
* libs/gst/base/gstcollectpads.h:
* libs/gst/base/gstpushsrc.c:
* libs/gst/base/gstpushsrc.h:
* libs/gst/dataprotocol/dataprotocol.c:
* libs/gst/dataprotocol/dataprotocol.h:
* libs/gst/net/gstnetclientclock.h:
* libs/gst/net/gstnettimeprovider.h:
Documentation updates.