soundtouch: update to 2.3.1

  2.3.1:

    * Adjusted cmake build settings and header files that cmake installs

  2.3.0:

    * Disable setting "SOUNDTOUCH_ALLOW_NONEXACT_SIMD_OPTIMIZATION" by
      default. The original purpose of this setting was to avoid performance
      penalty due to unaligned SIMD memory accesses in old CPUs, but that is
      not any more issue in concurrent CPU SIMD implementations and having
      this setting enabled can cause slight compromise in result quality.
    * Bugfix: soundtouch.clear() to really clear whole processing pipeline
      state. Earlier individual variables were left uncleared, which caused
      slightly different result if the same audio stream were processed
      again after calling clear().
    * Bugfix: TDstretch to align initial offset position to be in middle of
      correlation search window. This ensures that with zero tempo change
      the output will be same as input.
    * Bugfix: Fix a bug in TDstrectch with too small initial skipFract value
      that occurred with certain processing parameter settings: Replace
      assert with assignment that corrects the situation.
    * Remove OpenMP "_init_threading" workaround from Android build as it's
      not needed with concurrent Android SDKs any more.

  2.2:

    * Improved source codes so that compiler can autovectorize them more
      effectively. This brings remarkable improvement e.g. ARM cpus equipped
      with NEON vfpu: Bencmarked 2.4x improvement in execution speed in
      ARMv7l vs the previous SoundTouch version for both integer and
      floating point sample types.
    * Bugfix: Resolved bad sound quality when using integer sample types in
      non-x86 CPU
    * Bugfix: Fixed possible reading past end of array in BPM peak detection
      algorithm

(nia)