Show up with gcc -O0.

There's a few more but those are functions that need to be filled in.

Maybe this is a lost battle...

Sorry for the noise, downstream custom builders.  Please adjust.

Found and fixed a couple bugs.

Found a couple multithreading issues.  Marked them with "XXX-MT-bug".

Finally, unified!

Part of fixing https://github.com/behdad/harfbuzz/pull/605

This is a temporary hack just to avoid incorrect shaping results, pending proper support
for caching shape-plans with variation coordinates.

Fixes https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=1452#c5

CC https://github.com/behdad/harfbuzz/issues/139

clang's new -Wcomma compiler option warns about possible misuse of the
comma operator such as between two statements.

hb-common.cc:190:9 [-Wcomma] possible misuse of comma operator here
hb-ot-layout-gsubgpos-private.hh:345:30 [-Wcomma] possible misuse of
comma operator here
hb-shape-plan.cc:438:26 [-Wcomma] possible misuse of comma operator here

Shape-plan caching is not implemented.

Move the empty-buffer check from hb_shape_full() to hb_shape_plan_execute().

Reported by Simon Cozens.

Based on data from http://upstream-tracker.org/versions/harfbuzz.html
Resolves #103

Previously, when creating an object from inert inputs (eg:
"hb_font_create(hb_face_get_empty())") we returned the inert
empty object.  This is not helpful as there are legitimate
usecases to do that.

We now never return the inert object unless allocation failed.

Tests are revised to reflect.

The only effect is, if shaper_list was not NULL and no shaper was found,
we now don't insert anything into cache and return earlier.

Wasn't breaking out of loop, ouch!

http://www.mail-archive.com/debian-bugs-dist@lists.debian.org/msg1246370.html

Bug 77800 - cppcheck reports

Will fix by removing shape_plan->face completely.

Since our types are not associated with their methods, marking
constructors makes them inaccessible from bindings.  Undo for now.

Untested.

API additions:

	hb_segment_properties_t
	HB_SEGMENT_PROPERTIES_DEFAULT
	hb_segment_properties_equal()
	hb_segment_properties_hash()

	hb_buffer_set_segment_properties()
	hb_buffer_get_segment_properties()

	hb_ot_layout_glyph_class_t

	hb_shape_plan_t
	hb_shape_plan_create()
	hb_shape_plan_create_cached()
	hb_shape_plan_get_empty()
	hb_shape_plan_reference()
	hb_shape_plan_destroy()
	hb_shape_plan_set_user_data()
	hb_shape_plan_get_user_data()
	hb_shape_plan_execute()

	hb_ot_shape_plan_collect_lookups()

API changes:

	Rename hb_ot_layout_feature_get_lookup_indexes() to
	hb_ot_layout_feature_get_lookups().

New header file:

	hb-shape-plan.h

And a bunch of prototyped but not implemented stuff.  Coming soon.
(Tests fail because of the prototypes right now.)

https://bugs.freedesktop.org/show_bug.cgi?id=53233