Need to consider how we can better obey the "GASP" table in a font
to disable hinting and use greyscale as the default behaviour, not
just when desktop font hints are applied.
But I'm not sure we'd ignore an explicit "OFF" hint
And presently we ignore the hinting flag in GASP - only look
for greyscale - mostly because it affects metrics.
For fonts that say always do greyscale - at all sizes - this may be
a big clue that hinting isn't a good idea.
Needs more consideration to see if we should extend this and risk
the metrics change.
Also may want to explore adding the ability to explicitly request\
hinting (or not) as an API option, separate from GASP.