This reverts commit 5daf3bd4.

If other atexit callbacks try to destruct the objects we destruct
in atexit callbacks, bad things will happen.

I'll come up with some other way to catch premature destruction
of HB-owned objects.

Fixes https://github.com/behdad/harfbuzz/issues/618

Apparently calibri.ttf does this:
https://github.com/fonttools/fonttools/pull/1094#discussion_r148933791

Seems to work.  Yay!

Still to do: run kerning if GPOS doesn't have 'kern' feature.

Almost there.

Pushing this out early to catch bot errors since I'm using template tricks
we were not using in HarfBuzz before.

get_glyph_from_name() coming soon.

Such that client cannot accidentally destroy them, even though that
will be a bug in their code...

The get_glyph_from_name() is incorrect; needs fixing.

Turns out we already have support for “post” table, it just needed to be
activated and put in use.

Fixes https://github.com/behdad/harfbuzz/issues/474

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

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

Yay, works!

Fixes https://github.com/behdad/harfbuzz/pull/377

Should be all good now..

Almost there..

hb_font_get_glyph_extents now works for color bitmap fonts.
Currently only font having index format 1 and image format 17
is supported.

Ouch!

Fixes https://github.com/behdad/harfbuzz/issues/236
Fixes https://bugs.chromium.org/p/chromium/issues/detail?id=627953

To make a release...

Apparently some clients have reference-table callbacks that copy the table.
As such, avoid loading 'glyf' table which is only needed if fallback positioning
happens.