MKVToolNix 82.0.0 (64-bit)

What's new in this version:

New features and enhancements:
- Mkvmerge: Matroska reader: the "video alpha mode" track header property will be copied to the output file if present
- Mkvmerge: Matroska reader: the "video alpha mode" track header property will be reported in JSON identification mode as the track property `alpha_mode`
- Mkvmerge: Matroska reader: the file's timestamp scaling factor will be reported in JSON identification mode as the container property `timestamp_scale`
- Mkvmerge: MPEG transport stream reader: teletext subtitles intended for hearing impaired people (type 0x05) are now marked as such via the appropriate flag in the track headers
- Mkvmerge: file identification: the JSON identification output schema version has been bumped to 19
- Mkvmerge: added a new hack `always_write_block_add_ids` that can be used as a workaround for players that don't support the handling of missing "Block Addition ID" sub-elements of "Block More" elements in block additions properly. These are used for e.g. alpha channel data in VP9 with a "Block Addition ID" value of 1, which is also its default value.
- Mkvinfo: added support for the "video alpha mode" track header element
- Mkvpropedit, MKVToolNix GUI's header editor: added support for the "video alpha mode" track header property. In `mkvpropedit` it's called`alpha-mode`
- MKVToolNix GUI: multiplexer: when adding files the GUI can automatically enable the "hearing impaired" flag for audio and subtitle tracks if the file name contains the word "cc" or "sdh" delimited by certain characters (configurable). This feature is turned on by default
- MKVToolNix GUI: multiplexer: when scanning for Blu-ray playlists the GUI will now ignore playlists that are likely meant for menus. Currently the GUI considers this to be the case when a playlist contains the same item at least five times. This behavior can be turned off in the preferences

Fixed:
- Mkvmerge: MPEG transport stream reader: fixed a crash introduced in v81 that occurred when there was at least one PCM track that wasn't copied from the transport stream file
- Mkvmerge: when reading data from Matroska files damaged in a specific way, mkvmerge ended up trying to write various types of elements that aren't allowed to be written (so-called `EbmlDummy` elements as well as elements that don't have a value set) to the output file, which caused the underlying `libebml` library to abort. These types of broken elements are now filtered out.

Build system changes:
- Qt 5 is no longer supported. Qt 6 is now required for building MKVToolNix. This implies that the options to `configure` revolving around configuring Qt 5 or choosing between the two have been removed (e.g. `--disable-qt6`).
- Qt 6 detection: if detection fails, error messages from `qmake` can now be found in `config.log`
- Qt 6 detection: `configure` will only consider Qt 6.2.0 or newer, not 6.0.x or 6.1.y anymore, due to the lack of support for the multimedia module
- Qt 6 detection: `configure` will now fail to detect Qt 6 if the 'multimedia' module is not found by `qmake` (e.g. due to development packages not being installed)
- The bundled `fmt` library was updated to v10.1.1