All of init/medi/fina/isol and rlig implemented.

Let there be dragons... ⻯

Such it wouldn't apply to pointers accidentally.

Oops, thinko.

Adjust the list of marks before SARA AM that get the reordering
treatment.  Also adjust cluster formation to match Uniscribe.

With Wikipedia test data, now I see:

  - For Thai, with the Angsana New font from Win7, I see 54 failures out
    of over 4M tests  (0.00129107%).  Of the 54, two are legitimate
    reordering issues (fix coming soon), and the other 52 are simply
    Uniscribe using a zero-width space char instead of an unknown
    character for missing glyphs.  No idea why.  The missing-glyph
    sequences include one that is a Thai character followed by an Arabic
    Sokun.  Someone confused it with Nikhahit I assume!

  - For Lao, with the Dokchampa font from Win7, 33 tests fail out of
    54k (0.0615167%).  All seem to be insignificant mark positioning
    with two marks on a base.  Have to investigate.

If x is not constant, we cannot ASSERT_STATIC on it.

Specifically, don't apply 'init' if previous char is a joiner.

Fixes some more of Bengali.

This reorders glyphs within the cluster to a nominal order.  This should
have no visible effect on the output, but helps with testing, for
getting the same hb-shape output for visually-equal glyphs for each
cluster.

https://bugs.freedesktop.org/show_bug.cgi?id=50970

Oops.  hb_tag_t and OPENTYPE_TAG have different endianness.  Perhaps
something to add API for in hb-uniscribe.h

As reported by bashi.  Not tested.

Removes one more static-initialization.  A few more to go.

This was causing all object types to be non-POD and have static
initializers.  We don't need that!

Now, most nil objects just moved from .bss to .data.  Fixing for that
coming soon.

Makes debug output much more pleasant.

More to come, for APPLY, CLOSURE, etc.

We have varargs in the trace interface now.  To be used soon...

Users should #include <hb.h> (or hb-ft.h, hb-glib.h, etc), but
never things like hb-shape.h directly.  This makes it easier to
refactor headers later on without breaking compatibility.

Fixes build with MSVC.