Macro impl_ule_from_array

macro_rules! impl_ule_from_array {
    ($aligned:ty, $unaligned:ty, $default:expr, $single:path) => { ... };
    ($aligned:ty, $unaligned:ty, $default:expr) => { ... };
}

Given Self ($aligned), Self::ULE ($unaligned), and a conversion function ($single or Self::from_aligned), implement from_array for arrays of $aligned to $unaligned.

The $default argument is due to current compiler limitations. Pass any (cheap to construct) value.