Fallback to older API if OpenType variants are not available.

Defaults to auto.

Defaults to no.

Defaults to no.

We only want UCDN if we don't have any other Unicode provider.
I'm going to remove ICU from the list of default Unicode providers
as part of moving hb-icu into its own library.  As such, the only
providers will be UCDN and glib.

Will add a way to enable it later.

Bug 64878 - compile error with ICU but not ICU

Will add proper way to enable it later.

Add --with-graphite2.  Defaults to off.

If there's a mark ligating forward with non-mark, they were
inheriting the GC of the mark and later get advance-zeroed.
Don't do that if there's any non-mark glyph in the ligature.

Sample test: U+1780,U+17D2,U+179F with Kh-Metal-Chrieng.ttf

Also:
Bug 58922 - Issue with mark advance zeroing in generic shaper

Seems to work...

Mozilla Bug 873902 - Display Arabic text with diacritics is bad
https://bugzilla.mozilla.org/show_bug.cgi?id=873902

Fixes previous commit's test.

Failing now.

Bug 64476 - Typo in hb_set_t.get_min()