Fix issue with automake
[indic] Some scripts like blwf applied to pre-base characters

...while some don't!

Improved Bengali, Devanagari, Gurmukhi, Malayalam.

Updated numbers:

BENGALI: 353732 out of 354188 tests passed. 456 failed (0.128745%)
DEVANAGARI: 707307 out of 707394 tests passed. 87 failed (0.0122987%)
GUJARATI: 366349 out of 366457 tests passed. 108 failed (0.0294714%)
GURMUKHI: 60732 out of 60747 tests passed. 15 failed (0.0246926%)
KANNADA: 951030 out of 951913 tests passed. 883 failed (0.0927606%)
KHMER: 299070 out of 299124 tests passed. 54 failed (0.0180527%)
MALAYALAM: 1048134 out of 1048334 tests passed. 200 failed (0.0190779%)
ORIYA: 42320 out of 42329 tests passed. 9 failed (0.021262%)
SINHALA: 271666 out of 271847 tests passed. 181 failed (0.0665816%)
TAMIL: 1091753 out of 1091754 tests passed. 1 failed (9.15957e-05%)
TELUGU: 970555 out of 970573 tests passed. 18 failed (0.00185457%)
[myanmar] Apply abvm/blwm
[indic] Handle Avagraha

It can come either at the end(ish!) of the syllable, or independently.
When independent, it accepts a few bits and pieces.
[indic] Don't apply presentation features across syllables

More like Uniscribe...  We still allow user-defined features to
work across syllables, but not pres,blws,abs,psts,etc.

This "regressed" Sinhala numbers by 11.  These are cases were
there's Consonant followed by Ra,Halant,ZWJ at the of text.
The Ra,Halant,ZWJ ends up forming reph, which is wrong...
But before we were also ligating that reph with the previous
consonant.  That's even more wrong.  That's also what Uniscribe
does.

Current numbers:

BENGALI: 353732 out of 354188 tests passed. 456 failed (0.128745%)
DEVANAGARI: 707307 out of 707394 tests passed. 87 failed (0.0122987%)
GUJARATI: 366349 out of 366457 tests passed. 108 failed (0.0294714%)
GURMUKHI: 60732 out of 60747 tests passed. 15 failed (0.0246926%)
KANNADA: 951030 out of 951913 tests passed. 883 failed (0.0927606%)
KHMER: 299070 out of 299124 tests passed. 54 failed (0.0180527%)
MALAYALAM: 1048140 out of 1048334 tests passed. 194 failed (0.0185056%)
ORIYA: 42320 out of 42329 tests passed. 9 failed (0.021262%)
SINHALA: 271655 out of 271847 tests passed. 192 failed (0.070628%)
TAMIL: 1091753 out of 1091754 tests passed. 1 failed (9.15957e-05%)
TELUGU: 970555 out of 970573 tests passed. 18 failed (0.00185457%)
[indic] Apply 'kern' for all scripts except for Khmer in Uniscribe mode

Seems to better match Uniscribe.

Note: NotoSansTelugu-Regular has kern feature, so this fixes most of the
positioning failures there, except for the kern pairs blocked by a
(non-)joiner, in which case we (correctly) kern, but Uniscribe doesn't.
[tests] Remove Myanmar micro-font and test
[indic] Harmless reordering of Khmer features!
[indic] If Malayalam dot-reph formed a ligature, don't move it

Rachana-0.6 implements dot-reph by ligation, so we shouldn't move it.
Uniscribe doesn't either.  Test case:

  U+0D4E,U+0D1A,U+0D4D,U+0D1A,U+0D4D
[indic] Simplify reph logic

*Shouldn't* break anything.
[indic] Allow up to two syllable modifiers

Bug 70509 - Candrabindu+Visarga doesn't work in Devanagari
https://bugs.freedesktop.org/show_bug.cgi?id=70509

We categorize both bindus and visarga as syllable-modifiers.
OT spec doesn't actually say what characters go in the syllable
modifier category, and allows one.  We just allow up to two now.

Test case: U+0930,U+0941,U+0901,U+0903

Uniscribe currently doesn't support that and produces a
dotted circle.
[indic] Adjust cluster merging under uniscribe mode for Tamil

Apparently Uniscribe Tamil shaper doesn't ship chubby clusters
for Tamil.  Adjust to that.
[indic] Fix cluster merging of left matras

The merge_clusters there was totally broken.
[indic] More granular post-base cluster merging!
[otlayout] Minor
[arabic] Make ZWJ prevent ligatures instead of facilitating it

Unicode 6.2.0 Section 16.2 / Figure 16.3 says:

"For backward compatibility, between Arabic characters a ZWJ acts just
like the sequence <ZWJ, ZWNJ, ZWJ>, preventing a ligature from forming
instead of requesting the use of a ligature that would not normally be
used. As a result, there is no plain text mechanism for requesting the
use of a ligature in Arabic text."

As such, we flip internal zwj to zwnj flags for GSUB matching, which
means it will block ligation in all features, unless the font
explicitly matches U+200D glyph.  This doesn't affect joining behavior.
[indic] Misc harmless fixes!

First, we were abusing OT_VD instead of OT_A.  Fix that
but moving OT_A in the grammar where it belongs (which
is different from what the spec says).

Also, only allow medial consonants after all other
consonants.  This doesn't affect any current character.

Finally, fix Halant attachment in presence of medial
consonants.  Again, this currently doesn't affect any
sequence.

I lied.  There's Gurmukhi U+0A75 which is Consonant_Medial.
Uniscribe allows one of those in each of these positions:
before matras, after matras and before syllable modifiers,
and after syllable modifiers!  We currently just allow
unlimited numbers of it, before matras.
[indic] Improve Avagraha support in machine
[otlayout] Fix up recent Context matching change

Commit 6b65a76b40522a4f57a6fedcbdfc5a4d736f1d3c.  "end" was becoming
negative.  Was trigerred by Lohit-Kannada 2.5.3 and the sequence:
U+0CB0,U+200D,U+0CBE,U+0CB7,U+0CCD,U+0C9F,U+0CCD,U+0CB0,U+0C97,U+0CB3
Two glyphs were being duplicated.
[indic] Don't apply blwf before base under old-spec mode

Test case: U+09AC,U+09CD,U+09A6 with Lohit-Bengali 2.5.3.