[HarfBuzz] Test please!

[Behdad Esfahbod]

Hi,

I've pushed out a few changes:

  - Add fallback for space characters (without relying on compatibility
decomposition), with correct space width,

  - Misc low-hanging optimizations, specially when run with hb-ft or hb-ot
font funcs.  For custom funcs, it's now faster if implementations leave
functions undefined if that's the effect.  The one function particularly
optimized is glyph_h_origin().  It's better to leave it unimplemented if
that's possible.

Simon, this should speed up your use case more than anyone else's.  Can you
please share numbers?

I have some more hb-ot optimizations planned.  Will try to get them out.

If all looks good, and the fuzzer doesn't go red, I'll make a release tomorrow.

Cheers,
-- 
behdad
http://behdad.org/