New API:
+hb_aat_layout_has_substitution()
+hb_aat_layout_has_positioning()

Fixes https://github.com/harfbuzz/harfbuzz/pull/1346

Since it was pages and pages...

* hb_aat_get_feature_settings

Fixes https://github.com/harfbuzz/harfbuzz/issues/628

New API:
hb_coretext_font_create()

SFNSText has kerx table which apparently is applied.

This prepares the headers for exporting symbols using visibility
attributes or __declspec(dllexport), so that we do not need to maintain
symbols listing files, as this is what was and is done in GLib and GTK+.

Fixes https://github.com/behdad/harfbuzz/pull/40

On iOS CoreText and CoreGraphics are stand-alone frameworks

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.

Not sure if it's useful, but it was missing.

Does not attempt to handle clusters in a Uniscribe- or HarfBuzz-compatible way;
just returns the original string indexes that CT maintains. These may even be
out-of-order in the case of reordrant glyphs.

Also remove shaper_options argument to hb_shape_full().  That was
unused and for "future".  Let it go.

More shaper API coming in preparation for plan/planned API.

Users should #include <hb.h> (or hb-ft.h, hb-glib.h, etc), but
never things like hb-shape.h directly.  This makes it easier to
refactor headers later on without breaking compatibility.

I don't see how this function can be useful.

To be modified, a lot.