Macro cipher::impl_simple_block_encdec

macro_rules! impl_simple_block_encdec {
    (
        <$($N:ident$(:$b0:ident$(+$b:ident)*)?),*>
        $cipher:ident, $block_size:ty, $state:ident, $block:ident,
        encrypt: $enc_block:block
        decrypt: $dec_block:block
    ) => { ... };
    (
        $cipher:ident, $block_size:ty, $state:ident, $block:ident,
        encrypt: $enc_block:block
        decrypt: $dec_block:block
    ) => { ... };
}

Implement simple block backend