Update to 1.1 API (#165446).

Update to 1.1 API (#165446).

Original commit message from CVS:
* configure.ac:
* ext/musepack/Makefile.am:
* ext/musepack/gstmusepackdec.c: (gst_musepackdec_class_init),
(gst_musepackdec_init), (gst_musepackdec_dispose),
(gst_musepackdec_src_query), (gst_musepackdec_src_convert),
(gst_musepack_stream_init), (gst_musepackdec_loop),
(gst_musepackdec_change_state):
* ext/musepack/gstmusepackdec.cpp:
* ext/musepack/gstmusepackdec.h:
* ext/musepack/gstmusepackreader.c: (gst_musepack_reader_peek),
(gst_musepack_reader_read), (gst_musepack_reader_seek),
(gst_musepack_reader_tell), (gst_musepack_reader_get_size),
(gst_musepack_reader_canseek), (gst_musepack_init_reader):
* ext/musepack/gstmusepackreader.cpp:
* ext/musepack/gstmusepackreader.h:
Update to 1.1 API (#165446).