fix allFinite

Reference issue

What does this implement/fix?

DenseBase::allFinite can return 'false' for integer arrays, which is incorrect. std::numeric_limits<int>::infinity() is usually defined as 0. Actually its probably worse: since we implement this as abs(x) < infinity, this turns into abs(x) < 0, which is always false!

https://godbolt.org/z/4M96Gjxxb

Also added a check for gcc/clang/arm's __FINITE_MATH_ONLY__ macro. These platforms appear to consistently optimize std::isfinite to return true when compiled with -ffinite-math-only. Clang sets infinity to zero, which has the same effect described above. If this macro is set, allFinite will now return true for any expression.

Additional information