For some definition of improvement...

Unfortunately if the font has GPOS and 'mark' feature does
not position mark on dotted-circle, our inserted dotted-circle
will not get the mark repositioned to itself.  Uniscribe cheats
here.

If there is no GPOS however, the fallback positioning kicks in
and sorts this out.

I'm not willing to address the first case.

Not perfect, but so is fallback positioning in 2012...

No panic, we reeally insert dotted circle when it's absolutely broken.

Fixes most of the dotted-circle cases against Uniscribe. (for Devanagari
fixes 80% of them, for Khmer 70%; the rest look like Uniscribe being
really bogus...)

I had to make a decision.  Apparently Uniscribe adds one dotted circle
to each broken character.  I tried that, but that goes wrong easily with
split matras.  So I made it add only one dotted circle to an entire
broken syllable tail.  As in: "if there was a dotted circle here, this
would have formed a correct cluster."  That works better for split
stuff, and I like it more.

To be used in places we access buffer vars...

This will eventually allow us to skip marks, as well as (fallback)
attach marks to ligature components of fallback-shaped Arabic.
That would be pretty cool.  I kludged GDEF props in, so mark-skipping
works, but the produced ligature id/components will be cleared later
by substitute_start() et al.

Perhaps using a synthetic table for Arabic fallback shaping was a better
idea.  The current approach has way too many layering violations...

Looks better now...

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

This reverts commit 3e0a0397.

I know remember why that line is there :).

Previously, ccc=0 Thai / Lao marks were being
mispositioned.  Don't touch them.

D'oh.  Was working by pure chance :)).

Import PortableFontInstance and add shaper stub.

Fixes consonant-position with old-spec Malayalam.  Uniscribe seem to be
doing this.  Fixes below-base La (eg. Pa,H,La) with AnjaliNewLipi.ttf.
Doesn't regress new-spec or other scripts.