See discussion here:
https://github.com/behdad/harfbuzz/commit/81ef4f407d9c7bd98cf62cef951dc538b13442eb

There's no way to disable this fallback, but I don't think it would
be needed.  Let's hope for the best!

Fixes https://github.com/behdad/harfbuzz/issues/153

Fixes https://github.com/behdad/harfbuzz/issues/103

Fixes https://bugzilla.gnome.org/show_bug.cgi?id=541608
and cluster test.

Needed for upcoming merge-clusters fix.

TODO: Documentation.

Fixes: https://bugs.freedesktop.org/show_bug.cgi?id=71445

Fixes test-shape, and:
https://code.google.com/p/chromium/issues/detail?id=497578

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

Annotate the output parameter.

It should not be freed by the caller.

Fixes coretext notdef loop consisting of all default_ignorable glyphs

https://code.google.com/p/chromium/issues/detail?id=464755

In hb-coretext, when we were using scratch buffer for book-keeping,
a reverse_range() caused by the notdef-insertion loop could mess up
our log_clusters.  Ouch!

This is by no ways to promote non-Unicode encodings.  This is an entry
point that takes Unicode codepoints that happen to all be the first
256 characters and hence fit in 8bit strings.  This is useful eg in Chrome
where strings that can fit in 8bit are implemented that way, and this
avoids copying into UTF-8 or UTF-16.

Perhaps we should rename this to hb_buffer_add_codepoints8().  I'm also
curious if anyone would be really interested in hb_buffer_add_codepoints16().

Please discuss!

Minimal shaping works now!

After 763e5466, one doesn't
need to set flags for different pieces of text.  The flags now
are something the client sets up once, depending on how it
actually uses the buffer.  As such, don't clear it in
clear_contents().

Tests updated.

With this change, we now by default replace broken UTF-8/16/32 bits
with U+FFFD.  This can be changed by calling new API on the buffer.
Previously the replacement value used to be (hb_codepoint_t)-1.

Note that hb_buffer_clear_contents() does NOT reset the replacement
character.

See discussion here:

https://github.com/behdad/harfbuzz/commit/6f13b6d62daae4989e3cc2fe4b168e5c59650964

New API:

  hb_buffer_set_replacement_codepoint()
  hb_buffer_get_replacement_codepoint()

Like hb_buffer_add_utf32, but doesn't do any Unicode validation.
This is like what hb_buffer_add_utf32 used to be until a couple
commits ago.

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

Previously we were only setting this in hb_buffer_clear_contents(),
but set_length(0) is a valid way to reinitialize buffer to use with
new text.

Fixes last of scratch alignment warnings in hb-coretext.

Commit 6b65a76b.  "end" was becoming
negative.  Was trigerred by Lohit-Kannada 2.5.3 and the sequence:
U+0CB0,U+200D,U+0CBE,U+0CB7,U+0CCD,U+0C9F,U+0CCD,U+0CB0,U+0C97,U+0CB3
Two glyphs were being duplicated.

Previously we only supported recursive sublookups with
ascending indices.  We were also not correctly handling
non-1-to-1 recursed lookups.

Fix all that!

Fixes the three tests in test/shaping/tests/context-matching.tests,
which were derived from NotoSansBengali and NotoSansDevanagari
among others.

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

Add deprecated alias for old name.

Some infrastructures use DEBUG as a generic symbol.

Using a ragel machine.

The previous name was clashing with harfbuzz.old.  There are systems
that need to link both...

Clash-free now again.

Was causing assertion failure in shape_plan().

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.)