Log Message:
Switch to the version provided by the shntool people (which is also
the one that Gentoo uses). Closes PR 44533 by myself.

Changes since the last version we had in pkgsrc, 3.99-u4-b5:

version 3.99-u4-b5-s7
  + fixed compilation issue on big-endian systems [report: Michael Plotkin]

version 3.99-u4-b5-s6
  + fixed compilation issues with GCC 4.4 on some 64-bit systems [report: Eivind
 Eide]

version 3.99-u4-b5-s5
  + fixed long-standing 64-bit decompression crash [patch: Adam Nielsen]
  + fixed crash with pathnames longer than 256 characters [report: Kabakov Boris
]
  + fixed a compilation issue (don't pass -fno-common to yasm)

version 3.99-u4-b5-s4
  + include error reason with error code in mac.exe
  + automatically recalculate quick verify checksum when compressing, if
    necessary (e.g. piped encoding with foobar2000, or truncated WAVE file)

version 3.99-u4-b5-s3
  + reenabled quick-verification of APE files (via new '-q' option)

version 3.99-u4-b5-s2
  + show above version in mac.exe help screen (sN = shntool revision N)
  + added support for encoding WAVE data of unknown length (all files/pipes
    are now treated as unknown length; this forces mac.exe to write a seek
    table of maximum size regardless of input file size, adding ~30kb/file)

version 3.99-u4-b5-s1
  + added support for pipe encoding/decoding