This is a higher-priority shaper than default shaper ("ot"), but
only picks up fonts that have AAT "morx"/"mort" table.
Note that for this to work the font face's get_table() implementation
should know how to return the full font blob.
Based on patch from Konstantin Ritt.
Does not attempt to handle clusters in a Uniscribe- or HarfBuzz-compatible way;
just returns the original string indexes that CT maintains. These may even be
out-of-order in the case of reordrant glyphs.
Oleg Oshmyan
Konstantin Ritt
Behdad Esfahbod
Jonathan Kew