ext/raw1394/gstdv1394src.*: Added AV/C VTR control support needed for some cameras.

ext/raw1394/gstdv1394src.*: Added AV/C VTR control support needed for some cameras.

Original commit message from CVS:
* ext/raw1394/gstdv1394src.c: (gst_dv1394src_class_init),
(gst_dv1394src_init), (gst_dv1394src_set_property),
(gst_dv1394src_get_property), (gst_dv1394src_iso_receive),
(gst_dv1394src_discover_avc_node), (gst_dv1394src_change_state):
* ext/raw1394/gstdv1394src.h:
Added AV/C VTR control support needed for some cameras.
Added automatic port detection.
Added properties for selecting the channel.
The configure.ac script is not yet updated to reflect the
new libavc1394 and librom1394 dependencies.