Context manager.

Fixes shaping with Apple Chancery on 10.13 again.  In that font,
there was a terminator segment, that was tripping off sanitize().

This reverts commit ae8ed58a.

Apparently this broke Apple Chancery from OS X 10.12 :(.
Investigating...

This reverts commit 15905a2a.

This reverts commit bbdb6edb.

Have not encountered fonts needing this, but same reasoning as
for morx (see previos commit.)

With OS X 10.13 Apple Chancery fails to ligate if we limit each morx
sub-chain to its declared length.  Perhaps their newer compiler does
object-sharing across sub-chains.  Anyway, since that's a valid, if
unspecified, way to compile tables, remove enforcement.

Probably do the same with kern/kerx.

Line should start with "# ".

Broke in 8dcc1913

If sanitizer is left with another object, it wouldn't work.

Better fix coming soon.

The ones commented out in this change should've be passed :/
a closer look is needed.

Annotated OpenType Specification or aots, https://github.com/adobe-type-tools/aots
provides a set of tests for OpenType specification, this change add those tests in addition
to modified version of their HarfBuzz test runner for generating harfbuzz project specific tests.

Much more useful now. :)

Fixes https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=11526
Fixes https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=11522