libxmp: update to 4.7.0

libxmp: update to 4.7.0

A substantial release with many new features and module format
fixes since 4.6.3.

Highlights:
 * Increase maximum sampling rate (XMP_MAX_SRATE) to 768000.
 * xmp_seek_time now always seeks; new xmp_seek_time_frame for
   frame-accurate seeking.
 * New tempo factor APIs: xmp_set_tempo_factor_relative,
   xmp_get_tempo_factor, xmp_get_tempo_factor_relative.
 * New API define XMP_FORMAT_32BIT to enable 32-bit integer output.
 * New API defines XMP_INST_NO_DEFAULT_PAN, XMP_MARK_SKIP,
   XMP_MARK_END.
 * Add support for Pack-Ice depacking and Software Visions DMF
   (Apocalypse Abyss MOD variant).
 * Internal module time/duration calculations now use doubles.
 * Numerous bug fixes across MOD, XM, S3M, IT, RTM, MED, Funktracker,
   Imago Orpheus IMF, Liquid Tracker LIQ, DigiBooster Pro, IMS and
   other formats: sample default panning/volume corrections, effect
   memory and translation fixes, note edge cases.

Link: https://github.com/libxmp/libxmp/blob/libxmp-4.7.0/docs/Changelog
Signed-off-by: Daniel Golle <redacted>