Macro awint_internals::for_each_mut

macro_rules! for_each_mut {
    ($lhs:ident, $x:ident, $f:block, $clear_unused_bits:expr) => { ... };
    ($lhs:ident, $x:ident, $range:block $f:block, $clear_unused_bits:expr) => { ... };
}

f(x) is run on every digit from first to last.