Bug 58714 - Kannada u+0cb0 u+200d u+0ccd u+0c95 u+0cbe does not provide
same results as Windows8
https://bugs.freedesktop.org/show_bug.cgi?id=58714

Test with U+0CB0,U+200D,U+0CCD,U+0C95,U+0CBF and tunga.ttf.

Improves some scripts.  Improves Bengali too, but numbers
are up because we produce better results than Uniscribe for some
sequences now.

New numbers:
BENGALI: 353724 out of 354188 tests passed. 464 failed (0.131004%)
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: 951190 out of 951913 tests passed. 723 failed (0.0759523%)
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: 271662 out of 271847 tests passed. 185 failed (0.068053%)
TAMIL: 1091753 out of 1091754 tests passed. 1 failed (9.15957e-05%)
TELUGU: 970555 out of 970573 tests passed. 18 failed (0.00185457%)

See:
http://lists.freedesktop.org/archives/harfbuzz/2013-April/003101.html

This seems to generate much better, almost-perfect, positioning for
Arabic as well as Latin above marks.

Test with WinXP times.ttf and U+05D9,U+05B5.

Seems to be working just fine!

Lohit-Punjabi has a upem of 769!  We were losing one unit in our
code, and FreeType is losing another one...  Test with U+0A06.
Has an advance of 854 in the font.  We were producing 852.
Now we do 853, which is what FreeType is telling us.

See comments from caveat!  Seems to work fine.

This is useful for Javanese which has an atomically encoded pre-base
reordering Ra which should only be reordered if it was substituted
by the pref feature.

Currently unused.

Impact should be minimal and positive.

Currently unused.

Currently unused.

No functional change.

Both Indic and SEA seem to do it just fine, but SEA is much
simpler.

For scripts without an old/new spec distinction, use zero-context=false.
This changes behavior in Sinhala / Khmer, but doesn't seem to regress.
This will be useful and used in Javanese.

Previously we planted this into the mode used for Khmer.  There's not
really much in common between the two, so separate again.

Similar to 190c8f2b but for
Sinhala.

It's cheap.

Shouldn't change behavior at all, but is faster / more robust.