More instantiation problems under hpux

[Benjamin Kosnik]

> If you see the same failure mode (thus confirming my theory beyond
> i386 and one OS), then I could fix this test by making it more
> dynamic.  I think the main thing to test here is that the test case
> doesn't crash and that operator>> returns reasonable values whenever
> !is.fail().  Thus, instead of inferring from
> std::numeric_limits<T>::digits10 or
> std::numeric_limits<T>::max_exponent10 a guess at an input string size
> that fails, we could try to convert a small string to an FP.  If it
> converts, we could test that the FP number matches the number in the
> string we constructed within epsilon and then iterate with a larger
> input string.  The test only passes once we add the final digit that
> overflows (causing is.fail() to be true).

This would be acceptable, as it shows that one can get failed input due 
to size. If you want to do this, I would support such a change in the 
testsuite. 

As an aside: have we given up on getting sane limits behavior?

-benjamin