From upstream changelog (https://www.bunkus.org/videotools/mkvtoolnix/doc/ChangeLog):

• build system: Boost's »Math« library is now required.
• mkvmerge: bug fix: HEVC tracks which did not have an aspect ratio present in their sequence parameter set were copied incorrectly; the resulting sequence parameter set was invalid. Fixes #1081.
• mkvextract: bug fix: When extracting HEVC tracks mkvextract will use the same start code lengths that x265 uses (four bytes 0x00000001 for the first and video/picture/sequence parameter set NALs and three bytes 0x000001 for all others).
• mkvmerge: enhancement: File type identification will output a more detailed description of the DTS type for DTS audio tracks (DTS-HD Master Audio, DTS-HD High Resolution, DTS Express or just plain DTS). Implements #1109.
• mkvmerge: new feature: Implemented support for DTS Express.
• mkvmerge: bug fix: The number of channels in DTS tracks with more than six channels is now recognized correctly by parsing the DTS HD extensions, too. Fixes #1139.
• all: new feature: added a Swedish translation of the programs by Kristoffer Grundström (see AUTHORS).
• mkvmerge: bug fix: Fixed handling of the BITIMAPINFOHEADER extra data size handling during merging and extraction for codecs like HuffYUV.
• mkvmerge: bug fix: When appending unframed HEVC/h.265 tracks and setting the default duration the second and all following source parts will use the same default duration as set for the first part. Fixes #1147.
• mkvmerge: bug fix: enabled the use of tags in WebM files. Tagging elements not supported by the WebM specs are removed. Fixes #1143.
• mkvmerge: bug fix: fixed detection of audio tracks in QuickTime files whose FourCC code is unknown to mkvmerge.
• mkvmerge: bug fix: fixed detection of video tracks in QuickTime files whose FourCC code is unknown to mkvmerge.
• mkvextract: bug fix: Fixed VobSub file naming when mkvextract is built against Boost::Filesystem older than 1.50.0. Fixes #1140.
• mkvmerge: bug fix: fixed detection of Cinepak video tracks in QuickTime files.
• mkvmerge: bug fix: fixed detection of PCM audio tracks in QuickTime files using the »raw « FourCC.
• mkvmerge: bug fix: fixed detection of tracks in Flash Video files for which the headers do not signal a track.
• mkvmerge: bug fix: fixed a segfault in the Flash Video file format reader.
• mmg: The change making the window wider by default has been reverted.
• mkvmerge: bug fix: Fixed file type detection for MP3 files with big ID3 tags at the start of the file (e.g. if they contain cover images).
• mkvinfo (Qt interface): enhancement: implemented support for opening files via drag & drop.
• mkvmerge: enhancement: added an option (--engage no_delay_for_garbage_in_avi) for disabling deriving a delay from garbage in audio tracks in AVI files. Requested in #1137.
• mkvmerge: bug fix: The formula used for calculating the audio delay for garbage data at the start of tracks in AVI files has been fixed. Fixes #1137.