Only if the font doesn't support it.  Ie, this gives the user to
use non-Unicode codepoints as private values and return a meaningful
glyph for them.  But if it's invalid and font callback doesn't
like it, and if font has U+FFFD, show that instead.

Font functions that do not want this automatic replacement to
happen should return true from get_glyph() if unicode > 0x10FFFF.

Replaces https://github.com/behdad/harfbuzz/pull/27

Test passes now.

Currenty fails.  Ouch!

Previous code was broken logically, but harmless.

https://android-review.googlesource.com/#/c/100722/1/Android.mk

Fixes https://github.com/behdad/harfbuzz/pull/45

Apparently on travis-ci, bash is linked to dash, which doesn't
understand "let".  Failing tests were not being noticed.  See eg:

  https://travis-ci.org/behdad/harfbuzz/jobs/29544211

Don't rely on bash.

From http://github.com/behdad/ucdn

Useful for benchmarking, to avoid buffer serialization overhead (which
seems to by far dominate shaping!)

Supports ft and ot right now.  hb-view currently not rendering with ot.
Will fix after some clean up.

He's been my shadow for all Indic-related changes in the last
few months.

These were introduced in a498565c,
but IndicSyllabicCategory has had the correct value already, so the
special code was never needed.

Touch code just enough to preserve previous syllable structure
and functionality as closely as possible.  Many further cleanups
coming later.

There may be more.  There are members that are by definition
redundant or reserved and not needed, NOT what we *currently*
don't use.

I'm sure there's more...