devel/mtbl: Upgrade to version 1.4.0

The immutable sorted string table library project, mtbl 1.4.0, is
released. This release adds command-line options to support compression
levels in mtbl_merge, and a hex formatting option and a variety of
filtering options for mtbl_dump. Note that this release leaves the
MTBL file format unchanged. In detail:

• Add -l option to specify compression level for mtbl_merge.
• Add -x option to mtbl_dump to print data for the key and value each formatted with the length (8 digit hexadecimal), a colon, and then hex digit pairs separated by a dash.
• Minimum and maximum Zstd compression levels changed from hardcoded 1 and 22, respectively, to values defined by Zstd.
• Add -k and -v options to mtbl_dump to print only entries for which the key or value, respectively, matches the given prefix.
• Add -K and -V options to mbtl_dump to print only entries for which the length of the key or value, respectively, is greater than or equal to the given integer.

Sponsored by: Farsight Security, Inc.