Most unused.

Misc. table loading now properly automated.

Faster / more compact code.

Just blacklist based on table sizes like we do for other fonts.

This reverts commit 0c1b287b.

lwsync() is a full read/write-barrier.  That's all we need, never
need sync().  I'm not sure why an isync() was used in fetch_and_add,
but since that's a read-modify-write, I just changed it to have
lwsync() on both sides.

Since add_int and cas are both read-modify-write, I wonder if we
also need a barrier after them.

Originally, glib's atomic_get was implemented as "memory_barrier; load".
I copied this into cairo, fontconfig, and harfbuzz.  However, that's
wrong.  Correct way is "load; memory_barrier".  The details are long
and hard to fully grasp.  Best to read:

  https://www.kernel.org/doc/Documentation/memory-barriers.txt

Also see my report against GNOME:

  https://gitlab.gnome.org/GNOME/glib/issues/1449

Note that this is irrelevant if C++11-like atomic ops are available.