removed assert, fixes https://github.com/harfbuzz/harfbuzz/issues/1443

use double as CFF Number implementation

[aat] Expose hb_aat_layout_has_tracking API

New API:
+hb_aat_layout_has_substitution()
+hb_aat_layout_has_positioning()

Happened after 11d2f49a
since now nClasses is unsigned int...

Fixes spurious warnings like:
Fixes https://github.com/harfbuzz/harfbuzz/issues/1436

This reverts commit eb5ddd32.

Broke tests, badly.  To be investigated and reenabled.

Fixes spurious warnings like:
Fixes https://github.com/harfbuzz/harfbuzz/issues/1436

CFF/CFF2 subsetter

* Use nullptr instead of 0/NULL.

* Update test-name-table.cc

Fix ambiguous overload errors with old compilers

Now that we have 6daf45e0, revert cryptic hacks...

This reverts commit abd81ed4.
This reverts commit 9c6921c0.
This reverts commit d39760ca.
This reverts commit fedd8e6c.

Fixes https://github.com/harfbuzz/harfbuzz/issues/1374

The built-in operator takes signed int.  So, match it, such that
the built-in is never a better or equally-good match to our operator.
Fixes "ambiguous overload" errors from gcc 4.2 and VS 2008.

See https://github.com/harfbuzz/harfbuzz/issues/1374