[libstdc++-v3] Remove std::construct and std::destroy

[Joe Buck]

Jason writes:
> The HP implementation was a de facto standard; people wrote code against
> it.  In general, I consider breaking previously working code undesirable.
> Sometimes it's unavoidable, but I think folks have been too cavalier about
> tossing anything that's not in the standard without regard for usability.

Strongly agreed.  In any case, anything that was in in 3.0 can't come out
until at least 3.1, them's the rules.  Even then things should come out
for a good reason.

Anything that was well-documented on the SGI STL web site should stay in,
because lots of programs will use it.  There should be a way to make it
go away for strict conformance.

> > I think the goal should be to have standards-conformant headers, and 
> > older/deprecated headers available by request.
> 
> I'm amenable to this if the only thing a user needs to do is add something
> to CXXFLAGS.

Agreed.