[HarfBuzz] Support for optical 'opdb' feature(s)

[James Cloos]

A few years ago now¹, [sigh], a discussion which might have been on the
opentype list concluded that this is the ideal algorithm for breaking a
paragraph when using opentype features:

1) Characters -> initial glyphs
2) GSUB
3) GPOS (kerning for non-OpenType)
4) Division into breakable "syllables"
5) Line break decision
6) Repeat steps 1-3, just once

The opbd (and therefore ltbd and rtbd) lookups should occur as part of
step five.

-JimC

1]  About 4½ years ago, based on the file where I found my notes....

-- 
James Cloos <cloos at jhcloos.com>         OpenPGP: 1024D/ED7DAEA6