Makes more sense, optimization-wise.

I know...

This is apparently what Uniscribe does.  Test case is:

  SEEN FATHA TEH ALEF

with Arabic Typesetting.  Originally reported by Khaled Hosny.

Introduced in 99c26957.
Broken mark-mark and mark-ligature stuff.

Detected by clang and lots of cmdline options.

The old code was doing nothing.

Still got to find an example font+string that makes this matter, but
need this for fixing synthetic GDEF anyway.

The spec doesn't say contextual matching should be done this way,
and AOTS doesn't do it either.  It was inherited from old HarfBuzz.
Remove it.

This does not apply to the context matchings.

This regresses tests right now.  And we are not sure whether this is
the right thing to do for GPOS.  But we'll figure out.

This is to incorporate it into GSUB/GPOS processing.

Yay!

More to come, for APPLY, CLOSURE, etc.

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

Filling in.

I couldn't measure significant performance gains out of this; maybe
about 5% (with one million Malayalam strings).  Still, not bad.
But reminds me that optimizing this codebase without profiling first
is simply not going to work.  Oh well...

I have this function, but can't clean up it to my satisfaction.

We should be in good shape now.

Ouch!