std::pow implementation

[Robert Dewar]

> Defining a member function within a class declaration has exactly the
> same meaning.  And that has been documented in every manual since 1981.

Yes, we all agree that the as-if standard meaning is the same, that is
never in dispute. A compiler that ignores all inlining is perfectly
well in conformance, and that might make sense on a machine which favors
this approach, e.g. the transputer where a call is much faster than a jump.