manually adding cherry-picked commits from upstream:
a4875147a6f29b908162a81a2773a3cbab2433c8 by hunderteins <wegegeld@web.de> -  Add optimized AES and SHA1 routines
cca3c4e40e3765239afabea6d5682715b3f92849 by hunderteins <wegegeld@web.de> -  support XZ compressed kernels
8c63eb0cb591c6bae7db5d170581cbf5ab793d74 by hunderteins <wegegeld@web.de> -  support XZ compressed kernels part2
987c21b3c09f9c6d765ea7ecec8679087662d7ea by hunderteins <wegegeld@web.de> -  enable KBUILD_BUILD_USER and KBUILD_BUILD_HOST for custom version string