Always qualify calls to std::move()

Always qualify calls to std::move()

This quashes a new warning in clang++ 15, when std::move() (the
one-parameter version) is used as simply move(). There is a strong
recommendation from WG21 to avoid that.

Details here: https://reviews.llvm.org/D119670

It might be that we should not use that many move()s. I am not
competent to decide on that.

I also used this occasion to get rid of a spacial casing for C++11
that does not seem necessary after all.