The array query APIs now all do:

  - Return the total number of items
  - Take a start_offset, such that individual items can be fetched
  - The _count IN/OUT variable always has number of items written
    into the array upon return of the function

Separate OT headers also.

Such that we don't link to libstdc++.

It's not part of the standard and MSVC doesn't like it.  It makes the code
a lot less elegant than it used to be, but I think it should work now.

Thready-safety disabled in that case, until we add support for pthread, etc.
Fun...

Pointed out by Keith Stribley on HarfBuzz list.

Reported by Keith Stribley on HarfBuzz list.

Part of Bug 595539 - Regressions in rendering certain Thai sequences with
OpenType font

Part of Bug 595539 - Regressions in rendering certain Thai sequences with
OpenType font