Placement new-expression incorrect for overloaded operator& and operator new

[jwakely]

https://github.com/beman-project/Optional26/blob/bfeb9080c0d9c501965ae857a1decf7ed74686f5/include/Beman/Optional26/optional.hpp#L441

This needs to use (void*)std::addressof(value_)

[jwakely]

https://github.com/beman-project/Optional26/blob/bfeb9080c0d9c501965ae857a1decf7ed74686f5/include/Beman/Optional26/optional.hpp#L310

This one needs to vast to void* and use ::new

[steve-downey]

Also indicates missing test cases that ought not to have compiled, then.

[jwakely]

It's a very sneaky one to test for.

[steve-downey]

construct_at, which was needed for some constexpr cases, avoids the problem.

[steve-downey]

Holding off closing until the changes actually land here on main.