mkvtoolnix: update to 16.0.0

Version 16.0.0 "Protest":

New features and enhancements

* mkvmerge: MP4 reader: added support for Vorbis.

Bug fixes

* configure: the checks for libEBML and libMatroska have been fixed to require
  libEBML 1.3.5 and libMatroska 1.4.7 as intended.

* mkvmerge: AAC reader: mkvmerge will now emit an error message for AAC files
  whose header fields imply a sampling frequency or number of channels
  of 0.
* mkvmerge: AVC/h.264 ES parser: fixed the calculation of reference
  information for P and B frames. This also fixes some P frames being marked
  as B frames and vice versa.
* mkvmerge: AVC/h.264 ES parser: only non-key frames that have the NALU header
  field `nal_ref_idc` set to 0 will be marked as "discardable" in
  `SimpleBlock` elements.
* mkvmerge: HEVC/h.265: the generation of the HEVCC structure stored in
  `CodecPrivate` was wrong in two places: 1. the position of the number of
  sub-layers was swapped with reserved bits and 2. the VPS/SPS/PPS/SEI lists
  did not start with a reserved 1 bit.
* mkvmerge: output: the `doc type version` will be set at least to 2 if
  certain elements are written (`CodecState`, `CueCodecState`,
  `FlagInterlaced`).
* mkvmerge: output: the track header attributes `MinCache` and `MaxCache` will not be
  written anymore.
* mkvmerge: Matroska reader: the "key" and "discardable" flags of SimpleBlock
  elements will be kept as they are.
* mkvmerge: Matroska reader: if present in the file, the "white colour
  coordinate x" track header attribute was written to both "white colour
  coordinate x" and "white colour coordinate y" in the output file.
* mkvmerge: Opus output: mkvmerge will now put all frames with discard padding
  into their own block group.
* MKVToolNix GUI: header editor: removed the check for external modification
  when saving the file.
* MKVToolNix GUI: job queue: fixed calculation of total progress when
  automatic removal of completed is enabled.

(adam)