[HarfBuzz] Syriac shaping

[Behdad Esfahbod]

Hi list,

Don't remember if I reported here, but while doing the Arabic/Syriac/N'ko
shaper for harfbuzz, I discovered multiple bugs and deficiencies in OpenType
and Unicode standards.  I put a summary of those issues as well as test cases
for correct Syriac shaping behavior in this page:

  http://behdad.org/syriac

The page uses a webfont.  The harfbuzz results match that of ie9, which also
matches what I believe is the correct behavior.

Cheers,
behdad