Not functional change (expected!).

Fixes possible invalid read of two bytes.

Reported by Behzad Najjarpour Jabbari, Secunia Research.

Shouldn't be needed.  I have a hard time imagining this breaking any
legitimate use case.

Needed some rework of Extension table.  Hopefully I got it right, and
the new template usage doesn't break any compilers...

No functional change right now.

This makes a lot of code safer.  We only try modifying the object in one
place, after making sure it's safe to do so.  So, do a const_cast<> in
that one place...

Fixes https://github.com/behdad/harfbuzz/pull/51

Add buffer var allocation asserts to a few key places.

Simplifies hb_in_range() calls as the type can be inferred.
The rest is obsessiveness, I admit.

Normally if you want to, say, conditionally prevent a 'pref', you
would use blocking contextual matching.  Some designers instead
form the 'pref' form, then undo it in context.  To detect that
we now also remember glyphs that went through MultipleSubst.

In the only place that this is used, Uniscribe seems to only care
about the "last" transformation between Ligature and Multiple
substitions.  Ie. if you ligate, expand, and ligate again, it
moves the pref, but if you ligate and expand it doesn't.  That's
why we clear the MULTIPLIED bit when setting LIGATED.

Micro-test added.  Test: U+0D2F,0D4D,0D30 with font from:

[1]
https://code.google.com/a/google.com/p/noto-alpha/issues/detail?id=186#c29

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.

Patch from Jonathan Kew.

No functional change.

Shouldn't change behavior at all, but is faster / more robust.

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.

Not measurable by any means, but conceptually this is faster since
the mask matches more often than the digest.