This reverts commit 969ff3c7.

Not sure if we are going to use it.  But might incentivize us to.

Ouch!  We need a bigendian bot...

Fixes https://github.com/harfbuzz/harfbuzz/issues/1498

https://github.com/harfbuzz/harfbuzz/issues/1496#issuecomment-448818112

The ideas there are all part of hb-array.hh now.  To be determined how we
want to use generic iterator patterns.

Looks like operator hb_array_t<> from vector works here. :)

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

In file included from hb-face.cc:35:
hb-ot-cmap-table.hh: In member function 'void OT::CmapSubtableFormat4::_compiles_assertion_on_line_388() const':
hb-ot-cmap-table.hh:388: 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-open-type.hh:354: note: candidate 1: const Type& OT::UnsizedArrayOf<Type>::operator[](unsigned int) const [with Type = OT::IntType<short unsigned int, 2u>]
hb-ot-cmap-table.hh:388: note: candidate 2: operator[](const T*, int) <built-in>
hb-ot-cmap-table.hh: In member function 'void OT::CmapSubtableFormat4::_instance_assertion_on_line_388() const':
hb-ot-cmap-table.hh:388: 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-open-type.hh:354: note: candidate 1: const Type& OT::UnsizedArrayOf<Type>::operator[](unsigned int) const [with Type = OT::IntType<short unsigned int, 2u>]
hb-ot-cmap-table.hh:388: note: candidate 2: operator[](const T*, int) <built-in>
hb-face.cc: In function 'hb_blob_t* _hb_face_builder_data_reference_blob(hb_face_builder_data_t*)':
hb-face.cc:650: 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-vector.hh:81: note: candidate 1: Type& hb_vector_t<Type, PreallocedCount>::operator[](unsigned int) [with Type = hb_face_builder_data_t::table_entry_t, unsigned int PreallocedCount = 32u]
hb-face.cc:650: note: candidate 2: operator[](T*, int) <built-in>
hb-face.cc:650: 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-vector.hh:81: note: candidate 1: Type& hb_vector_t<Type, PreallocedCount>::operator[](unsigned int) [with Type = hb_face_builder_data_t::table_entry_t, unsigned int PreallocedCount = 32u]
hb-face.cc:650: note: candidate 2: operator[](const T*, int) <built-in>
hb-face.cc:651: 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-vector.hh:81: note: candidate 1: Type& hb_vector_t<Type, PreallocedCount>::operator[](unsigned int) [with Type = hb_face_builder_data_t::table_entry_t, unsigned int PreallocedCount = 32u]
hb-face.cc:651: note: candidate 2: operator[](T*, int) <built-in>
hb-face.cc:651: 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-vector.hh:81: note: candidate 1: Type& hb_vector_t<Type, PreallocedCount>::operator[](unsigned int) [with Type = hb_face_builder_data_t::table_entry_t, unsigned int PreallocedCount = 32u]
hb-face.cc:651: note: candidate 2: operator[](const T*, int) <built-in>

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

Profiling showed that type conversions were adding considerable cycles in time
spent doing text shaping.

The idea is to optimize it using native processor instructions to help Blink
layout performance.

Doing further investigation revelead that compilers may not use the
proper instruction on ARM 32bits builds (i.e. REV16).

One way to insure that the generated ASM was ideal for both gcc/clang
was using __builtin_bswap16.

Added bonus is that we no longer need to test for CPU architecture.

Context manager.

This reverts commit bbdb6edb.

Affects morx/kerx run-time only currently.  Will adjust their sanitize next.

Not sure I've marked all such structs.  To be done as we discover.

Fixes https://github.com/harfbuzz/harfbuzz/issues/1300

So, our fallback static_assert cannot be had more than once per line
of source.

Bots not happy with using "this" inside assertion...

This reverts 26566448