Was good idea, but with C++ types with constructor/destructor, was getting in
the way as compiler was destructing those items where it was not desired.
Since C++ does not allow zero-sized arrays, just remove it...

I'm thinking about dropping it to zero, but that needs slight code changes.

* reimplement ByteStr as byte_str_t based on hb_ubytes_t

Unuse start_embed<ByteStr>
Also renamed SubByteStr to byte_str_ref_t
More renaming to come

* substr renamed to str_ref in line with its type byte_str_ref_t

* uncamelize non-table struct names

* uncamelized non-struct types OpCode etc

* add byte_str_t copy ctor

* test

* test2

* undo tests

* fix bot failure

* undo the previous change

* fixed tabs, added inline

* Revert "fixed tabs, added inline"

This reverts commit 21163c30e9d18759414f7fe2518628241599f039.

* fix tabs

To fix older compilers again (this was the case in hb_array_t).

hb-ot-layout-common.hh:1353: note: candidate 2: operator[](T*, int) <built-in>
hb-ot-layout-common.hh:1354: error: ISO C++ says that these are ambiguous, even though the worst conversion for the first is better than the worst conversion for the second:
hb-iter.hh:63: note: candidate 1: Item& hb_iter_t<Iter, Item>::operator[](unsigned int) const [with Iter = hb_array_t<const OT::IntType<short unsigned int, 2u> >, Item = const OT::IntType<short unsigned int, 2u>]
hb-ot-layout-common.hh:1354: note: candidate 2: operator[](T*, int) <built-in>
hb-ot-layout-common.hh: In member function 'bool OT::ClassDef::serialize(hb_serialize_context_t*, hb_array_t<const OT::IntType<short unsigned int, 2u> >, hb_array_t<const OT::IntType<short unsigned int, 2u> >)':
hb-ot-layout-common.hh:1490: error: ISO C++ says that these are ambiguous, even though the worst conversion for the first is better than the worst conversion for the second:
hb-iter.hh:63: note: candidate 1: Item& hb_iter_t<Iter, Item>::operator[](unsigned int) const [with Iter = hb_array_t<const OT::IntType<short unsigned int, 2u> >, Item = const OT::IntType<short unsigned int, 2u>]
hb-ot-layout-common.hh:1490: note: candidate 2: operator[](T*, int) <built-in>

hb_array_t is its own iterator...

Should only be done by subclass.

Starting to get the hang of when take which.