Fixes all except for cmap.  To be done separately.

Part of https://github.com/harfbuzz/harfbuzz/issues/1146

https://github.com/harfbuzz/harfbuzz/pull/1254

https://github.com/harfbuzz/harfbuzz/commit/d941f66c75fe26f909b1ba248535cc372bbde851#commitcomment-31076011

This is like hb_script_t.

We had this exposed as unsigned int since 2.0.0 release in two APIs,
as well as hb_ot_layout_get_size_params() from earlier.
But since no one uses those (right?!), let's just fix this now.

Accept Mac Latin name entries as ASCII as well.

It assumes all names are encoded in UTF16-BE.  Other than that, and not
listing languages correctly, it's *supposed* to work.

Fix a bug in CBDT sanitize, and redundant check in avar.

Sorry for the noise, downstream custom builders.  Please adjust.

Such a headache that Windows defines UINT8, ...; Just prefix it.

(And prevent it from happening in the future.)

Not functional change (expected!).

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...

Avoids USHORT, SHORT, ULONG, LONG clashes with Windows API.