This patch adds optimized implementations of MORUS-640 and MORUS-1280,
utilizing the SSE2 and AVX2 x86 extensions.

For MORUS-1280 (which operates on 256-bit blocks) we provide both AVX2
and SSE2 implementation. Although SSE2 MORUS-1280 is slower than AVX2
MORUS-1280, it is comparable in speed to the SSE2 MORUS-640.
Signed-off-by: Ondrej Mosnacek <omosnacek@gmail.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>