MKVToolNix v76.0 “Celebration”

# Version 76.0 "Celebration" 2023-04-30

## Important notes

* mkvmerge: removed the option `--blockadd`. Removing block additional data is
  not possible anymore, as it is often required for proper decoding. Part of
  the implementation of #3511.

## New features and enhancements

* mkvmerge: JSON file identification: added a child element called
  `num_index_entries` to the `properties` track element containing the number
  of index entries found for a track. Currently only implemented for Matroska
  files where it contains the number of cue points. See #3510.
* mkvmerge: the maximum block addition ID track header value is now calculated
  automatically from both the existing mappings & the actually used block
  additions in the block groups. Part of the implementation of #3511.
* mkvmerge: Matroska reader: when reading WebM files that use block additions
  with ID 4 (HDR for VP9) an appropriate block addition mapping will be
  created automatically. Part of the implementation of #3511.
* mkvmerge: MP4 reader: the title/movie name meta data (content of the
  `udta.meta.ilst.©nam` atom) will now be copied over as the segment title
  track header attribute. Part of the implementation of #3475.
* mkvmerge: MP4 reader: the comment & encoder meta data (content of the
  `udta.meta.ilst.©cmt` & `….©too` atoms) will now be copied over as global
  tags `COMMENT` & `ENCODER` respectively. Part of the implementation of
  #3475.
* mkvmerge, MKVToolNix GUI's multiplexer: added an option to stop processing
  after the primary video track ends called `--stop-after-video-ends`. This
  discards any remaining packets of other tracks. Part of the implementation
  #3506.
* MKVToolNix GUI: only on Windows: the GUI now uses Qt's "Fusion" style
  instead of the deprecated "Windows Vista" style. The advantage is that as of
  Qt 6.5 the "Fusion" style properly supports Windows 10's & 11's dark
  application mode. The Windows binaries are now built with said Qt
  version. Therefore the option to disable the dark mode has been
  removed. Fixes #3264 and likely others.
* MKVToolNix GUI: multiplexer: automatically setting the destination file
  name: added an option in the preferences for using the first source file's
  directory name instead of its file name as the basis for the destination
  file name. Implements #3512.
* MKVToolNix GUI: multiplexer: double-clicking on certain columns in the
  "tracks" view will now toggle them directly (columns "Default track" &
  "Forced track") or activate the corresponding control (columns "Language",
  "Name" & "Delay"). Double-clicks on other columns will do what they've done
  before, too: toggling the "Copy item" state. Implements #3513 & others.
* MKVToolNix GUI: the dialog for editing language tags is now created only the
  first time the user wants to edit a language tag & cached afterwards instead
  of creating a new instance each time. This makes subsequent uses instant.

## Bug fixes

* mkvmerge: mkvmerge will now only try to probe for VobSubs if the name of the
  file to identify ends in either `.idx` or `.sub`, preventing
  mis-identification of other file types if VobSubs with the same base name
  exist in the same directory. Fixes #3508.
* mkvmerge: AC-3: mkvmerge will now skip certain types of garbage data (16
  bytes starting with 0x01 0x10) that can occur before each sync frame,
  fixing the file not being identified as AC-3. Fixes #3484.
* mkvmerge: Matroska reader: when reading files that use block additions with
  IDs other than 1 (e.g. 4 for HDR for VP9) the IDs will now be kept & written
  to the output file. Before no ID would be written, effectively using 1 as
  that's the default value for the corresponding element. Part of the
  implementation of #3511.
* mkvmerge: mkvmerge will no longer write block addition mappings or the max
  block addition ID track header elements when creating a WebM file as those
  elements aren't supported there. Part of the implementation of #3511.
* mkvpropedit: fixed replacing chapters & tags in files that don't contain
  tracks. Fixes #3498.