Fixes crashes reported with left matra under
non-uniscribe-bug-compatibilty mode.

Improves Bengali and Gurmukhi.  Malayalam regressed a bit.  We will deal
with that later.

This is a bunch of hacks for now.

Improves Bengali a bit.

Fixes 20 out of 48 failing Oriya tests.  Failure rate down to 0.066% now.

Oriya failures down from 0.65% to 0.20%.

Fixes most Malayalam failures.  Down from 1.6% to 0.38% now.  Fixes a
few more in other scripts too.

Apparently this was approved in Feb 2012.  No font yet.

Now that we break syllables on Halant,ZWNJ, this code can be simplified.

That's really what Uniscribe does, and explains a lot of pecularities of
Halant,ZWNJ before the base.

Sent Telugu from 1% failures to 0.03%.  Improved Kannada and Malayalam
slightly.  Fixed half of Bengali, and did NOT break anything!

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

Fixes some more of Bengali.

Not tuned, just copied from step 2.  Fixes another 0.5% of Kannada
failures.  1% to go.

Fixes a few Devanagari, half of remaining Kannada failures, quarter for
Telugu, and others slightly improved or unchanged.

Fixes 5 Devanagari failures, and no regressions.

Brings down failures with Lohit-Telugu from 57% to 1.40%.

Kannada failures down from 3.5% to 2.93%.

It's not in IndicSyllabicCategory.txt.  Fixes most of Gurmukhi failures.
Failures down from 7.7% to 0.222%!

For Khmer, all consonants are subjoining.  No need to look in the font.
We were looking in the wrong order anyway.

Fixes 1.5% more failures for Telugu, 2% for Kannada.
Breaks one test in Devanagari.

Fixes another 5% of Kannada failures.

Fixes most failures of Oriya, and improves others a bit.

Following what the spec says.

Brings down Telugu failures from 40% to 3.75%, and Kannada failures from
44% to 10%.  Does NOT affect other scripts' test results.

POS_BASE can disappear if base ligated backward.  Define base as last
with position not after base.

Fixes a few hundred of Sinhala failures with Iskoola Pota.

In Sinhala, Reph is formed only explicitly, by the presence of a ZWJ.

Really this time.

Fixes another 18 Khmer tests.

For example: U+915,U+200c,U+93f

Fixes last Tamil failure!

Tamil has only about 150 failures now!

It's a visual Repha.

Still not positioning logical Repha as occurs in Malayalam.

Another 200 Khmer failures fixed.  547 to go.  That's better than
Devanagari!

Down another 500 or so Khmer failures!

In such scripts (ie. Khmer), a ZWJ/ZWNJ shouldn't stop the search for
base.  So, instead just choose the first consonant as base directly.

Test sequence:
U+1798,200c,U+17C9,U+17D2,U+179B,U+17C1,U+17C7