Fixes https://bugzilla.mozilla.org/show_bug.cgi?id=644184
among others.

Shapers now can request segmented feature application by calling
add_gsub_pause() or add_gpos_pause().  They can also provide a
callback to be called at the pause.  Currently the Arabic shaper
uses pauses to enforce certain feature application.  The Indic
shaper can use the same facility to pause and do reordering in the
callback.

The test/object test is passing again, instead of deadlocking.

The Win32 definitions for LONG, ULONG, etc conflicts with
hb-open-type.h.  Avoid that by making sure hb-object-private.h
and hb-open-type.h are not included in the same compilation unit.

Patch from Bradley Grainger.

Based on patch by Bradley Grainger.

With this, test/object is now passing.  Yay!

Now that we use C++ for all source code, lets benefit from it!

The hb_be_int16/32_get/put/eq() macros grow code size if replaced with
inline functions, so leave them as is.

Would have been nice if gcc had warned...

Makes way for adding arbitrary user_data support.

Unused right now.

So we can liberally use the simple features of C++ that parts of the
codebase is already using.

It's just sugar.

Since we now assert thos in hb-private.h, the int types cannot be wrong.
(Except for when someone else includes hb-common.h in a very broken
configuration, but that's not our problem!)

Plus, we don't use inline in the public headers, so remove that too.

__LOC__ was renamed to _HB__LOC__ in cd7555 but the corresponding
change wasn't made in hb-private.h.