- [varLib.mutator] Implement IUP optimization (#969).
- [_g_l_y_f.GlyphCoordinates] Changed ``__bool__()`` semantics to match those
of other iterables (e46f949). Removed ``__abs__()`` (3db5be2).
- [varLib.interpolate_layout] Added ``mapped`` keyword argument to
``interpolate_layout`` to allow disabling avar mapping: if False (default),
the location is mapped using the map element of the axes in designspace file;
if True, it is assumed that location is in designspace's internal space and
no mapping is performed (#950, #975).
- [varLib.interpolate_layout] Import designspace-loading logic from varLib.
- [varLib] Fixed bug with recombining PairPosClass2 subtables (81498e5, #914).
- [cffLib.specializer] When copying iterables, cast to list (462b7f86).