Macro ulps_eq

macro_rules! ulps_eq {
    ($lhs:expr, $rhs:expr $(, $opt:ident = $val:expr)*) => { ... };
    ($lhs:expr, $rhs:expr $(, $opt:ident = $val:expr)*,) => { ... };
}

Approximate equality using both the absolute difference and ULPs (Units in Last Place).