ext/gdk_pixbuf/gstgdkpixbuf.*: Make work with packetised/framed input (e.g. png-in...

ext/gdk_pixbuf/gstgdkpixbuf.*: Make work with packetised/framed input (e.g. png-in-quicktime). Use

Original commit message from CVS:
* ext/gdk_pixbuf/gstgdkpixbuf.c: (gst_gdk_pixbuf_sink_setcaps),
(gst_gdk_pixbuf_class_init), (gst_gdk_pixbuf_init),
(gst_gdk_pixbuf_flush), (gst_gdk_pixbuf_chain):
* ext/gdk_pixbuf/gstgdkpixbuf.h:
Make work with packetised/framed input (e.g. png-in-quicktime). Use
GST_ELEMENT_ERROR when we return GST_FLOW_ERROR. Add some
GST_DEBUG_FUNCPTR here and there. Use GST_LOG for recurring
debug messages. Fix boilerplate macros.