[vsipl++] compiler warnings

[Stefan Seefeld]

Jules Bergmann wrote:

> I don't see any harm in adding such a macro (it would have to be called 
> VSIP_IMPL_UNREACHABLE_RETURN of course).

Right.

> What unreachable returns are you seeing?  Yesterday, two from dist.hpp 
> (line 623 and line 633) showed up quite a bit, but that was about it.

These, as well as map.hpp:413, map.hpp:509, map.hpp:458. They were
issued each time the templates were instantiated, or so it appears.
We need to silence them both, to make our test pass (well, we could
filter them out from inside the test harness), as well as to make
users happy.

Regards,
		Stefan