Macro assert_eq_approx

macro_rules! assert_eq_approx {
    ($actual:expr, $expected:expr, fn = $func:expr $(,)?) => { ... };
    ($actual:expr, $expected:expr, fn = $func:expr, $($t:tt)+) => { ... };
    ($actual:expr, $expected:expr $(,)?) => { ... };
    ($actual:expr, $expected:expr, $($t:tt)+) => { ... };
}

Asserts that two values are approximately equal

For comparison, this uses ApproxEq::approx_eq by default, or the provided fn = ... function.