Merge pull request #1 from Cyan4973/dev

Dev
Merge pull request #3 from Cyan4973/dev

Dev
Merge pull request #5 from Cyan4973/dev

Dev
Merge pull request #8 from Cyan4973/dev

Dev
renamed bench.c into xxhsum.c
tune xxhsum display messages
Fix issue 22 : use XXH_malloc() & XXH_free()
Fix issue 23 : xxhsum output to stdout