We always push a pause at the end such that each lookup falls in exactly
one pause_map_t.  Now, only if I can find a better name for that...

Saves another 3 / 4 percent with Amiri.

Not measurable by any means, but conceptually this is faster since
the mask matches more often than the digest.

Wasn't correct with the new combiner.  I should add it back somehow,
but for now the digests seem to be working very well...

Was unused.

Make Amiri rendering faster a whopping 45% again!  Speends up pretty
much anything I tested.

Correctly this time.

We were not initializing the digests properly and as a result they were
being initialized to zero, making digest1 to never do any useful work.

Speeds up Amiri shaping significantly.

This reverts commit 3d1b66a3.

The calculations were buggy.  It's not worth optimizing right now.

Useful for profiling shapers.

Just to be sure it's not punishing the old shaper performance
numbers.  Doesn't seem to have a measurable effect.

See thread "an issue regarding discrepancy between Korean and Unicode
standards" on the mailing list for the rationale.  In short: Uniscribe
doesn't, so fonts are designed to work without it.

This almost reverts 2761e8a6,
but only if under MINGW32, so it doesn't affect MSVC.

Testing shows that this is closer to what Uniscribe does.

Reported by Khaled Hosny:

"""
commit 56800027
...
This commit is causing a regression with Amiri, the string “هَٰذ” with
Uniscribe and HarfBuzz before this commit, gives:

	[uni0630.fina=3+965|uni0670.medi=0+600|uni064E=0@-256,0+0|uni0647.init=0+926]

But now it gives:

	[uni0630.fina=3+965|uni0670.medi=0+0|uni064E=0@-256,0+0|uni0647.init=0+926]

i.e. uni0670.medi is zeroed though it has a base glyph GDEF class.
"""

The test case is U+0647,U+064E,U+0670,U+0630 with Amiri.

https://bugs.webkit.org/show_bug.cgi?id=113796

We don't use gthread anymore, remove leftovers.

See discussion on mailing list.

After the Ngapi hackfest work, we were assuming that fonts
won't use presentation features to choose specific forms
(eg. conjuncts).  As such, we were using auto-joiner behavior
for such features.  It proved to be troublesome as many fonts
used presentation forms ('pres') for example to form conjuncts,
which need to be disabled when a ZWJ is inserted.

Two examples:

	U+0D2F,U+200D,U+0D4D,U+0D2F with kartika.ttf
	U+0995,U+09CD,U+200D,U+09B7 with vrinda.ttf

What we do now is to never do magic to ZWJ during GSUB's main input
match for Indic-style shapers.  Note that backtrack/lookahead are still
matched liberally, as is GPOS.  This seems to be an acceptable
compromise.

As to the bug that initially started this work, that one needs to
be fixed differently:

  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

New numbers:

BENGALI: 353689 out of 354188 tests passed. 499 failed (0.140886%)
DEVANAGARI: 707305 out of 707394 tests passed. 89 failed (0.0125814%)
GUJARATI: 366349 out of 366457 tests passed. 108 failed (0.0294714%)
GURMUKHI: 60706 out of 60747 tests passed. 41 failed (0.067493%)
KANNADA: 951030 out of 951913 tests passed. 883 failed (0.0927606%)
KHMER: 299070 out of 299124 tests passed. 54 failed (0.0180527%)
LAO: 53611 out of 53644 tests passed. 33 failed (0.0615167%)
MALAYALAM: 1048102 out of 1048334 tests passed. 232 failed (0.0221304%)
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%)
TIBETAN: 208469 out of 208469 tests passed. 0 failed (0%)

Ubuntu doesn't (or didn't until recently?) ship icu pkg-config
files.  That's quite unfortunate.  Work around it.

Bug 57608 - ICU Detection fallback for non-pkgconfig systems

That flag is redundant, deprecated, and ignored since April 2011.
From FreeType git log:

commit 8c82ec5b17d0cfc9b0876a2d848acc207a62a25a
Author: Behdad Esfahbod <behdad@behdad.org>
Date:   Thu Apr 21 08:21:37 2011 +0200

    Always ignore global advance.

    This makes FT_LOAD_IGNORE_GLOBAL_ADVANCE_WIDTH redundant,
    deprecated, and ignored.  The new behavior is what every major user
    of FreeType has been requesting.  Global advance is broken in many
    CJK fonts.  Just ignoring it by default makes most sense.

    * src/truetype/ttdriver.c (tt_get_advances),
    src/truetype/ttgload.c (TT_Get_HMetrics, TT_Get_VMetrics,
    tt_get_metrics, compute_glyph_metrics, TT_Load_Glyph),
    src/truetype/ttgload.h: Implement it.

    * docs/CHANGES: Updated.