Macro fixed_hash::impl_hash_conversions

macro_rules! impl_hash_conversions {
    ($a: ident, $a_size: expr, $b: ident, $b_size: expr) => { ... };
}

Implements conversion to and from hash types of different sizes. Uses the last bytes, e.g. From<H256> for H160 uses bytes 12..32 CAUTION: make sure to call with correct sizes and the bigger type first or bad things will happen!