MKVToolNix (64-bit)

What's new in this version:

New features and enhancements:
- mkvmerge: chapters: mkvmerge can now read chapters from DVDs if the user specifies the path to a DVD folder structure via the `--chapters …` parameter. By default chapters from the first title will be imported. This can be changed by append `:<title number>` to the file/directory name in the `--chapters …` argument, e.g. `--chapters /srv/dvds/BigBuckBunny/VIDEO_TS:3`. This feature requires mkvmerge to have been built with the `libdvdread` library. Part of the implementation of #2808.
- mkvmerge: added `--engage append_and_split_flac` that enables mkvmerge to append and split FLAC tracks, restoring pre-v45 behavior. The resulting tracks will be broken: the official FLAC tools will not be able to decode them and seeking will not work as expected.
- MKVToolNix GUI: multiplexer: added support for mkvmerge's new support for reading chapters from DVDs if both have been built with the `libdvdread` library. Part of the implementation of #2808.
- MKVToolNix GUI: multiplexer: when deriving languages from file names the GUI will now look for simplified language names instead of the full ones (e.g. instead of looking for "Greek, Modern (1453-)" it would simply look for "Greek").
- MKVToolNix GUI: multiplexer: the options in the "additional command-line options" dialog are now sorted alphabetically. Additionally the `--append-mode` option has been added as one of the only missing global options
- MKVToolNix GUI: chapter editor: the chapter editor can now read chapters from DVDs if MKVToolNix has been build with the `libdvdread` library
- MKVToolNix GUI: header editor: added an option in the preferences for displaying all date & time values in UTC instead of the local time zone

Bug fixes:
- all: fixed a crash when using the `MTX_LOGGER=file` syntax for logging debug messages without specifying a file name to log to. It will now log to a file called `mkvtoolnix-debug.log` in the system's default temporary directory, as initially intended.

Build system changes:
- The library will be used if found via `pkg-config`. If it is found, support for reading chapters from DVDs will be enabled in `mkvmerge` and the MKVToolNix GUI. Part of the implementation of #2808.
- Boost's Date/Time, Lexical Cast, Range, Range Adaptors, Tri-Bool, Variant libraries are not used anymore
- MKVToolNix now requires a C++ compiler & standard library that support the following features of the C++17 standard: "`std::variant`", "`std::gcd`". For the GNU Compiler Collection (gcc) this means v7 or newer; for clang it means v4 or newer — the same versions required by earlier MKVToolNix versions.
- MKVToolNix now requires version 6.1.0 of fmtlib or later for the `fmt::to_string` function and bugfixes to the formatting of floating point numbers. If a system-wide version is installed that's older, the bundled copy will be used.
- The bundled version of fmtlib has been updated to release 6.2.1