Originally we fixed those in 79d1007a.
However, fonts like MongolianWhite don't have GDEF, but have IgnoreMarks
in their LigatureSubstitute init/etc features.  We were synthesizing a
GDEF class of mark for Mongolian Variation Selectors and as such the
ligature lookups where not matching.  Uniscribe doesn't do that.

I tried with more sophisticated fixes, like, if there is no GDEF and
a lookup-flag mismatch happens, instead of rejecting a match, try
skipping that glyph.  That surely produces some interesting behavior,
but since we don't want to support fonts missing GDEF more than we have
to, I went for this simpler fix which is to always mark
default-ignorables as base when synthesizing GDEF.

Micro-test added.

Fixes rest of https://bugs.freedesktop.org/show_bug.cgi?id=65258

Enable tests that were disabled before, and adjust one test,
and add more tests.

Though, looks like gcc was smart enough to produce the same code
before...

Simplifies hb_in_range() calls as the type can be inferred.
The rest is obsessiveness, I admit.

It's both faster and produces smaller code.  Now I feel stupid for
not writing it this way before.

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.