mkvtoolnix: updated to 48.0.0

Version 48.0.0 "Sick Of Losing Soulmates" 2020-06-27

New features and enhancements

* mkvmerge: AC-3: file identification will report AC-3 tracks encoded in Dolby
  Surround EX as codec "AC-3 Dolby Surround EX".
* MKVToolNix GUI: multiplexer: on new installations the GUI will now recognize
  all known ISO 639-2 language codes in file names by default instead of only
  the top 100 of languages by native speakers.
* MKVToolNix GUI: multiplexer: on new installations the list of "often used
  languages" will by default only contain certain agnostic ones ("multiple
  languages", "no linguistic content", "reserved for local use", "uncoded
  languages"), "English" and the default user interface language. The "list of
  spoken languages by native speaks" isn't used anymore.
* MKVToolNix GUI: header editor: added an option to remove all attachments to
  the tree context menu.
* MKVToolNix GUI: while the GUI is running it will remember the last page that
  was selected when the preferences dialog is closed. Upon re-opening the
  preferences that page will be selected by default.

Bug fixes

* mkvmerge: fixed a segmentation fault when exiting prematurely due to write
  errors such as the destination having run out of space.
* mkvmerge: DTS: fixed wrong channel count for DTS tracks with XCh
  extensions.
* mkvmerge: MPEG TS reader: fixed detecting h.264/AVC and h.265/HEVC tracks
  that consist of only a single frame.
* mkvmerge: MPEG TS reader: fixed handling of unbounded PES sizes for tracks
  that consist of only a single PES packet.
* mkvmerge: MPEG TS reader: PGS subtitle tracks are now exempt from the
  "detect bogus subtitle timestamps" heuristic which could lead to some PGS
  subtitles not being timestamped correctly. Symptoms were that they were
  shown at the wrong time or that they were shown indefinitely.
* mkvmerge: MPEG TS reader: when reading MPLS playlists the start timestamps
  of a play items were handled wrong: all the timestamps of packets read were
  compared to that start timestamp, dropping those packets whose timestamps
  were smaller than the play item's start timestamp. The correct behavior is
  to accept all packets as soon as the first one with a timestamp equal to or
  larger than the play item's start timestamp is encountered. This could
  result in PGS subtitle entries located right at the start of the play item
  being garbled/lost as they consist of multiple PES packets for which some
  timestamps are often slightly smaller.
* mkvmerge: MPEG TS reader: when reading MPLS playlists mkvmerge will no
  longer read the whole M2TS files they reference, processing only the packets
  lying inside the timestamp range given by the playlists's play item's start
  & end timestamps. Instead mkvmerge will use the index information present in
  corresponding clip information (CLPI) files in order to seek to the nearest
  file position of the play item's start timestamp. Additionally mkvmerge will
  simply stop processing a file once the end timestamp is seen. This change
  greatly speeds up processing files from which only small portions must be
  read.
* mkvmerge: WavPack: fixed support for files created by v5 of the
  program. Checksums, DSD audio data and non-standard sampling rates are
  handled correctly. Patch by David Bryant.
* MKVToolNix GUI: multiplexer: fixed the cursor being positioned wrong after
  entering or pasting characters that aren't allowed in file names into the
  "destination file" control.

Build system changes

* libEBML v1.4.0 and libMatroska v1.6.0 are now required.

Other changes

* The source code repository's main development branch was renamed to `main`.


(adam)