ext/musepack/gstmusepackdec.c: Some cleanups; pause task when push fails.

ext/musepack/gstmusepackdec.c: Some cleanups; pause task when push fails.

Original commit message from CVS:
* ext/musepack/gstmusepackdec.c: (gst_musepackdec_base_init),
(gst_musepackdec_init), (gst_musepackdec_send_newsegment),
(gst_musepackdec_handle_seek_event),
(gst_musepackdec_get_src_query_types), (gst_musepackdec_src_query),
(gst_musepack_stream_init), (gst_musepackdec_sink_activate),
(gst_musepackdec_sink_activate_pull), (gst_musepackdec_loop),
(gst_musepackdec_change_state):
Some cleanups; pause task when push fails.