Prior to this change the function `FT_Error FT_Done_Face(FT_Face *)` was
called through a pointer with the signature `void (void *)` resulting in
undefined behaviour.

Fixes https://github.com/behdad/harfbuzz/pull/271

Part of https://github.com/behdad/harfbuzz/issues/277

Addressing Nikolay Sivov reviews on harfbuzz mailing list

No longer noticeable memory increase on create/destroy iterations,
highly better than current state of uniscribe backend

This reduces memory consumption of my iterated font create/destroy cycle test
significantly and makes it much better than uniscribe backend even

With help of
https://dxr.mozilla.org/mozilla-central/source/gfx/2d/NativeFontResourceDWrite.cpp

Fixes https://github.com/behdad/harfbuzz/issues/267

Fixes https://github.com/behdad/harfbuzz/issues/255

Fixes https://github.com/behdad/harfbuzz/issues/218

From draft update to USE.

Fixes https://github.com/behdad/harfbuzz/issues/253

Hopefully we got the logic right.

Fixes https://github.com/behdad/harfbuzz/issues/243

With javatext.ttf, the reodering medial Ra gets its advance width
zero'ed in Uniscribe implementation, and the font adds the advance
back.  Our Indic shaper does not do that, but USE does.  So, route
Javanese through USE.  That's what Microsoft does anyway.  Test:

  U+A9A5,U+A9BA

This also seems to fix the following sequence, and variations thereof:

  U+A99F,U+A9C0,U+A9A2,U+A9BF

Fixes https://github.com/behdad/harfbuzz/issues/251

These are frozen, so good time to add.

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.

Fixes https://github.com/behdad/harfbuzz/issues/237

Note that Uniscribe enforces a certain syllable order.  We don't.
But with this change, I get all of the tibetan contractions pass
with Microsoft Himalaya font.

Fixes https://github.com/behdad/harfbuzz/issues/234

To make room to remember Mongolian Free Variation Selectors.
Part of fixing https://github.com/behdad/harfbuzz/issues/234