AIX print -0.0 , inf, nan differently, which are causing the test
failures. We are OK for most other tests.
This patch remove the tests related these limitations conditionally on AIX,
so that we can enable the other tests to avoid losing test coverage.
The general direction is:
if strings don't differ between environments, keep the string literal "INF" and the padding, instead of folding them into variables.
I think the general direction in earlier reviews (I think it might have been in D120022), is that for these strings that don't differ between environments, keep the string literal "INF" and the padding, instead of folding them into variables.
So here, the only thing that really differs is inf vs INF, then we would only need that single variable, but keeping the literal strings for everything else.