RFC: initial support to add X11 algorithm

This is basically integration work to bring the X11 algorithm from elmad's fork of ig0tik3d's fork of your version of cpu-miner back upstream.

While elmads version only works with AES_NI, I made it a compile-time option (c.f. Makefile.am and configure.in). I extracted the relevant bits from cpu-miner.c (the fork is based on an older version and this the file diverged a bit) and basically copied the folder x5 and x6.

X11 without AES_NI works fine for me, however, enabling support for this CPU extension, I only get bad hashes - dunno why, yet.