----------------------------
- [instancer] Recalc OS/2 AvgCharWidth after instancing if default changes (3317).
- [otlLib] Make ClassDefBuilder class order match varLib.merger's, i.e. large
classes first, then glyph lexicographic order (3321, 3324).
- [instancer] Allow not specifying any of min:default:max values and let be filled
up with fvar's values (3322, 3323).
- [instancer] When running --update-name-table ignore axes that have no STAT axis
values (3318, 3319).
- [Debg] When dumping to ttx, write the embedded JSON as multi-line string with
indentation (92cbfee0d).
- [varStore] Handle > 65535 items per encoding by splitting VarData subtable (3310).
- [subset] Handle null-offsets in MarkLigPos subtables.
- [subset] Keep East Asian spacing fatures vhal, halt, chws, vchw by default (3305).
- [instancer.solver] Fixed case where axisDef < lower and upper < axisMax (3304).
- [glyf] Speed up compilation, mostly around ``recalcBounds`` (3301).
- [varLib.interpolatable] Speed it up when working on variable fonts, plus various
micro-optimizations (3300).
- Require unicodedata2 >= 15.1.0 when installed with 'unicode' extra, contains UCD 15.1.