std::pow implementation

[Robert Dewar]

> It is an "as-if" rule only because that is the way it is described in
> standardese.   In the C++ community, we do care about history and
> documented behaviour.   You won't change that, just because you want
> C++ inline to have a less language specific meaning.

It's the only possibloe description in standardese here.

The point is that appealing to the ISO standard (as you did a few msgs ago)
is not particularly helpful, since the standard really has nothing to say.
This is a matter that must be decided, as with any code generation issue,
on the basis of what is pragnmatically best.