Before we were just relying on the compiler inlining them and not
leaving a trace in our public API.  Try to fix.  Hopefully not
breaking anyone's build.

Based on suggestion from Andrew Glass.

Test: U+0F40,0FC6,0F83

Currently fails.

commit b5a0f69e
Author: Behdad Esfahbod <behdad@behdad.org>
Date:   Thu Oct 17 18:04:23 2013 +0200

    [indic] Pass zero-context=false to would_substitute for newer scripts

    For scripts without an old/new spec distinction, use zero-context=false.
    This changes behavior in Sinhala / Khmer, but doesn't seem to regress.
    This will be useful and used in Javanese.

The *intention* was to change zero-context from true to false for scripts that
don't have old-vs-new specs.  However, checking the code, looks like we
essentially change zero-context to always be true; ie. we only changed things
for old-spec, and we broke them.  That's what causes this bug:

  https://bugs.freedesktop.org/show_bug.cgi?id=76705

The root of the bug is here:

  /* Use zero-context would_substitute() matching for new-spec of the main
   * Indic scripts, but not for old-spec or scripts with one spec only. */
  bool zero_context = indic_plan->config->has_old_spec || !indic_plan->is_old_spec;

Note that is_old_spec itself is:

  indic_plan->is_old_spec = indic_plan->config->has_old_spec && ((plan->map.chosen_script[0] & 0x000000FF) != '2');

It's easy to show that zero_context is now always true.  What we really meant was:

  bool zero_context = indic_plan->config->has_old_spec && !indic_plan->is_old_spec;

Ie, "&&" instead of "||".  We made this change supposedly to make Javanese
work.  But apparently we got it working regardless!  So I'm going to fix this
to only change the logic for old-spec and not touch other cases.

Disables any cluster-merging.  Added for testing purposes while
we investigate what kind of API to add for this.

Fixes https://bugs.freedesktop.org/show_bug.cgi?id=75384

Fixes https://bugs.freedesktop.org/show_bug.cgi?id=74491

Fixes https://bugs.freedesktop.org/show_bug.cgi?id=74490

As requested by Martin Hosken on the list.

Many GCC versions don't define __arm64__

Fixes https://github.com/behdad/harfbuzz/pull/35

On iOS CoreText and CoreGraphics are stand-alone frameworks

Fixes warnings.
https://bugzilla.mozilla.org/show_bug.cgi?id=984081

...to avoid an unused function warning; see mozilla bug https://bugzilla.mozilla.org/show_bug.cgi?id=984081.

Not tested.

This is a higher-priority shaper than default shaper ("ot"), but
only picks up fonts that have AAT "morx"/"mort" table.

Note that for this to work the font face's get_table() implementation
should know how to return the full font blob.

Based on patch from Konstantin Ritt.

Useful for Android / Chrome / etc when ICU is built in the same
library as harfbuzz itself.

Apparently some modern fonts have proper GPOS mark positioning
tables, but undesirable precomposed forms!  See thread
"Hebrew composition to presentation forms" and:

  http://tex.stackexchange.com/questions/156775/having-trouble-with-vowel-positioning-in-ezra-sil-xelatex

Test case: U+fb1d,05d9,05b4

Seems like configure.ac is already able to handle it.