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.

All passing now.

Fixes test-set.c

Fails now.  Fixing.

If you say:

  hb-shape font.ttf text --output-file out.txt

This was previously failing:

  Unknown output format `txt'; supported formats are: TEXT / JSON

Now we simply fallback to TEXT if no explicit format was requested.

Test sequence is simple: U+0D4E,U+0D15.  The doth-reph should be
reordered to after the Ka.

https://bugzilla.redhat.com/show_bug.cgi?id=799565

Bug 54948 - Undefined symbols: "operator delete(void*)" "operator
new(unsigned long)" "___cxa_pure_virtual"

Looks at alternate location now.

To fix FeatureParam issues.  No actual fix yet, just plumbing.