Compiles to same vector code, just a bit simplier.
vec_crc32.c is now identical to upstream
(https://github.com/antonblanchard/crc32-vpmsum/).

C code by Rogerio Alves <rogealve@br.ibm.com>

This implemention has been tested on big endian too.
Signed-off-by: Daniel Black <daniel@linux.ibm.com>