Some clang versions define static_assert as a macro apparently, so we cannot
redefine it...

This reverts commit 94bfea0c.
This reverts commit 4e626278.

"Unused private member" warning turned error.  ugh.

So we don't accidentally break it again.

...like UnsizedArrayOf<>.

This fixes a class of crasher bugs, mostly with color and AAT tables.  We
cannot use nullable offsets to varsized data that does not declare min_size,
because it's nost safe to use our fixed-size null pool for types that have
their size external.  So, use non_null'able offsets for these.

A further enhancement would be to make use of min_size in Null<> itself.
Will try that after.

Does NOT apply user-selected features.  But at least now enables
correct subtables.

An offset to unsized arrayis not safe to be redirected to our fixed-sized
null pool.  Plus, we want to reject, not repair, bad-looking dfonts.

Not sure how I didn't add before...

Just to disagree with myself re being done with this code...

Previously, ResourceForkHeader was defined as 30 bytes, having the typeCountM1 as last member.
There was a mysterious offset-by-2 in the code, derived from FontTools and JDK code this was
ported from.

In testing, I observed that typeListZ offset is actually 28.  Suggesting that the typeCountM1
does NOT actually belong to ResourceForkHeader, but belongs to the array itself.  Adjusting for
that resolves the mystery +2 offset hack, so everything is clean and good now.

This, concludes my dfont hacking.  The code looks great now, and I'm happy to leave it.
Fuzzers might disagree though, we will see!

So it doesn't accidentally match our templates, etc.

Offset 0 is not null in this context.

I don't think I broke anything.  Fuzzers will let me know..

I have no way to authoritatively know, but looks like test font only has one
face.  So, adjust test expectation instead.

Fixes https://github.com/harfbuzz/harfbuzz/pull/1085