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

Too bad this doesn't help MSVC 2008 build, as explicit operators are
C++11.

Much more useful now. :)

Towards consolidating all array bsearch/...

Towards consolidating all array bsearch/...

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

Disable copy/assign on them, as they shouldn't.

Make constructor / destructor call init_shallow/fini_shallow,
and make those idempotent.  So, these three can be constructed
on stack now and no init/fini call is needed.  As such,
hb_auto_t<> is not needed anymore.  I'll remove that separately.

Add pointer cast operator and plus operator.

From bungeman.

Fixes https://github.com/harfbuzz/harfbuzz/pull/1314

This reverts commit de0b9a46.
This reverts commit 921f0e6e.

Annnnd, revert.  MSVC doesn't like it.

Hopefully this fits fine with SFINAE with all our compilers.

Ugly, but...
Fixes https://github.com/harfbuzz/harfbuzz/issues/1227

Sorry for the noise, downstream custom builders.  Please adjust.