* Add characters:
  - LATIN SMALL LETTER SIDEWAYS O (`U+1D11`);
  - LATIN SMALL LETTER SIDEWAYS OPEN O (`U+1D12`);
  - LATIN SMALL LETTER SIDEWAYS O WITH STROKE (`U+1D13`);
  - LATIN SMALL LETTER SIDEWAYS U (`U+1D1D`);
  - LATIN SMALL LETTER SIDEWAYS DIAERESIZED U (`U+1D1E`);
  - LATIN SMALL LETTER SIDEWAYS TURNED M (`U+1D1F`);
  - MODIFIER LETTER SMALL SIDEWAYS U (`U+1D59`);
* Make user build plans' variants inheritable (#1345).
* Add top-cut variants of `1` (#1354).