configure.ac: Check for wavpack version and define WAVPACK_OLD_API if necessary.

configure.ac: Check for wavpack version and define WAVPACK_OLD_API if necessary.

Original commit message from CVS:
Patch by: Sebastian Dröge <slomo at circular-chaos.org>
* configure.ac:
Check for wavpack version and define WAVPACK_OLD_API if
necessary.
* ext/wavpack/Makefile.am:
* ext/wavpack/gstwavpackcommon.c: (gst_wavpack_read_header),
(gst_wavpack_read_metadata):
* ext/wavpack/gstwavpackcommon.h:
* ext/wavpack/gstwavpackdec.c: (gst_wavpack_dec_base_init),
(gst_wavpack_dec_class_init), (gst_wavpack_dec_init),
(gst_wavpack_dec_finalize), (gst_wavpack_dec_format_samples),
(gst_wavpack_dec_clip_outgoing_buffer), (gst_wavpack_dec_chain),
(gst_wavpack_dec_sink_event), (gst_wavpack_dec_change_state),
(gst_wavpack_dec_request_new_pad), (gst_wavpack_dec_plugin_init):
* ext/wavpack/gstwavpackdec.h:
* ext/wavpack/gstwavpackenc.c: (gst_wavpack_enc_class_init),
(gst_wavpack_enc_init), (gst_wavpack_enc_finalize),
(gst_wavpack_enc_set_wp_config):
* ext/wavpack/gstwavpackparse.c: (gst_wavpack_parse_base_init),
(gst_wavpack_parse_finalize), (gst_wavpack_parse_class_init),
(gst_wavpack_parse_index_get_entry_from_sample),
(gst_wavpack_parse_scan_to_find_sample),
(gst_wavpack_parse_handle_seek_event),
(gst_wavpack_parse_create_src_pad):
* ext/wavpack/gstwavpackstreamreader.c:
* ext/wavpack/gstwavpackstreamreader.h:
Port to new/official wavpack API, don't use API that was exported
in wavpack header files and in the lib but meant to be private, at
least not for recent wavpack versions; misc. 'cleanups' (#347443).