Previously, we were NOT actually recomposing Hangul Jamo.  We do now.
The two lines in:

test/shaping/texts/in-tree/shaper-default/script-hangul/misc/misc.txt

Now render the same with the UnDotum.ttf font.  Previously the second
linle was rendering boxes.

We can also start applying OpenType Jamo features later.  At this time,
I have no idea how the 'ljmo', 'vjmo', 'tjmo' features are supposed to
work.  Maybe someone can explain them to me?

In this mode we try composing CCC=0 with CCC=0 characters.  Useful for
Hangul.

No logical difference so far.

Composed, and decomposed, of the same text.

In preparation for Hangul shaper.

This is the most convenient way to browse scripts.

Cross-checked with Mark Davis's spreadsheet at http://goo.gl/x9ilM

As requested by Jonathan Kew.

We need to devise a better mechanism to choose which scripts to
pass through the Indic shaper.  Moreover, currently we are storing
data for some scripts in the Indic shaper that are not even going
through that shaper.  Need to find a better way...

From:
https://bugzilla.mozilla.org/show_bug.cgi?id=662055

Makes number of failures against Uniscribe with hi_IN dictionary from
OO.o to go down from 6334 to 4290.  Not bad for a one-line change!

Mozilla Bug 729626 - ASAN: heap-buffer-overflow HTML

The OSAtomicAdd32Barrier operator returns the new value, we want the
old value.

So, apparently there's no atomic int 'get' method on Apple.  You have to
add(0) to get.  And that's not const-friendly.  So switch inert-object
checking to a non-atomic get.  This, however, is safe, and a negligible
performance boost too.

Apparently it can't be implemented on OS X.  We weren't using it anyway.

By defining HB_NO_MT.

Also, only warn once per missing MT feature support.

Mozilla Bug 666661 - gfx/harfbuzz/src/hb-prive.h - compiler warnings on mac

Patch from Jonathan Kew.

Bug 662055 - advanced Hebrew diacritics are shown correctly only in
particular order.

Patch from Jonathan Kew.

Bug 662055 - advanced Hebrew diacritics are shown correctly only in particular order