libxmp: update to 4.7.2

libxmp: update to 4.7.2

4.7.1:
- fixed crashes and other bugs in the smix API; rewrote the smix WAV
  loader to support stereo samples
- fixed XM channel default instrument memory, IT high offset/oversized
  offset handling, MED synth/hybrid finetune conversion
- fixed Magnetic Fields Packer track loading and optimised tracks
- fixed path_join when loading a module from the current directory
- fixed loading truncated/broken Startrekker AM instruments and their
  precedence, envelope, P.FALL and FQ toneporta bugs
- allowed Archimedes MUSX modules to load with a broken SDAT instrument
  subchunk
- fixed various -fsanitize=shift-base warnings

4.7.2:
- fixed loading Startrekker modules from memory/handle/callbacks
- fixed a cmake build failure for certain Apple targets (e.g. tvOS)
- fixed stb-vorbis floor1 inverse_db_table indexing, a missing part of
  the CVE-2019-13220 fix

Signed-off-by: Daniel Golle <redacted>