Implemented as a hack for now.  Myanmar failures down from 23 to 15.

MYANMAR: 1123868 out of 1123883 tests passed. 15 failed (0.00133466%)

The remaining 15 cases are all where the syllable is wrong according to
the OpenType spec.  We insert dottedcircle.  Uniscribe fails to do that,
but it also fails to reorder the prebase-reordering medial-Ra.  So it
gets it wrong.

Myanmar failures down from 51% to 0.00204648%!

MYANMAR: 1123860 out of 1123883 tests passed. 23 failed (0.00204648%)

Before, when matching ligatures, we never skipping over base / liga
glyphs even if that was what the LookupFlags asked for.

Fixed now.  We carefully reviewed all instances of this, and tested with
Amiri as well as some Indic scripts, and are confident that this should
NOT break anyone's fonts.  It's also how Uniscribe does it, from what
we can tell.

In aticipation of upcoming changes.

Was breaking reph formation logic when the Ra is the only consonant.
Devanagari regression fixed.  Down to 57 failures again.  Ouch.

Before, for most scripts, we were not trying to recompose two characters
if the second one had ccc=0.  That fails for Myanmar where U+1026
decomposes to U+1025,U+102E, both of which have ccc=0.  However, we do
want to try to recompose those.  We now check whether the second is a
mark, using general category instead.

At the same time, remove optimization that was conflicting with this.

[Let the Ngapi hackfest begin!]

This reverts commit 01013a0f.

Conflicts:
	config.h.in

Same argument as previous commit.

This reverts commit fab7a71f.

Conflicts:
	src/hb-ot-shape-complex-indic-machine.hh

Keeping that generated file in-tree causes problems with processes like
tinderbox  that automatically fetch and build harfbuzz.  It's harder to
bootstrap harfbuzz now (as was previously), but I'm willing to give this
another chance and see how it goes.

As reported by Peter Breitenlohner:

I think this is a very bad idea because ENV is used to specify a startup
file to be read by some/all shells.

Thanks to Khaled for spotting it.

Now, it looks like this breaks Cygwin again.  Have to figure out what's
going on.

Looks like Cygwin / MSVC declare it that way, and it still works on
MinGW32 cross.

This reverts commit 0a492357.

Enables code on more compilers.

Based on fontconfig patch from Raimund Steger.

Sample crash:

0  _hb_graphite2_shaper_face_data_destroy (data=0xffffffffffffffff)
    at ../../src/hb-graphite2.cc:129
1  0x00007ffff4271d7d in hb_graphite2_shaper_face_data_ensure (
    face=<optimized out>) at ../../src/hb-shaper-list.hh:35
2  hb_shape_plan_plan (shaper_list=<optimized out>, num_user_features=0,
    user_features=0x0, shape_plan=0xf7b490) at ../../src/hb-shaper-list.hh:35
3  hb_shape_plan_create (face=<optimized out>, props=<optimized out>,
    user_features=0x0, num_user_features=0, shaper_list=<optimized out>)
    at ../../src/hb-shape-plan.cc:108
4  0x00007ffff4272c93 in hb_shape_plan_create_cached (face=0x10cf2b0,
    props=0x11980d8, user_features=0x0, num_user_features=<optimized out>,
    shaper_list=0x0) at ../../src/hb-shape-plan.cc:283

For example: u0c9a u0ccd u0c9a u0ccd with Lohit.  See:

https://bugs.freedesktop.org/show_bug.cgi?id=59118

If in a MarkPos table, a base has no anchor for a particular mark class,
return NULL such that the subsequent subtables get a chance at it.

Test case:
hb-shape ./EBGaramond12-Regular.otf ἂ --features="ss20","smcp"

The previous name was clashing with harfbuzz.old.  There are systems
that need to link both...

Clash-free now again.

Apparently helps with MSVC compilation.

Not sure if this is the most desired behavior.  It's the most easily
defined though.

Previous logic was just wrong.

As reported by Jonathan Kew.