Initial commit of lookup-table AES implementation

In need of optimization and cleanup.  Uses 32-bit integers arithmetic
and seems to run very quickly (100k key expansions + encrypts in 3.88
= 400K/s encryption).  Based on p7zip's optimized C implementation.
crypto.aes: <sliced-groups> is now just <groups>, add a missing using.
unmaintained: fix <sliced-groups> to be <groups>.