Although this already works in most cases in non-kvm serenity cases the
cosh and other math function tend to return incorrect values for
Infinity. This makes sure that whatever the underlying cosh function
returns Math.cosh conforms to the spec.
The native C++ < and > operators won't handle this correctly, so the
result was different depending on the order of arguments. This is now
fixed by explicitly checking for positive and negative zero values.
Fixes#6589.
