fix R16 support on velvet and new_hash macro

From [Kelly's patch](https://gist.github.com/kellymclaughlin/b27755fc6eda6b55c373) , with  Stanchion ( https://github.com/basho/stanchion/pull/64 ) and velvet ( https://github.com/basho/velvet/pull/12 ).

CC: https://github.com/basho/velvet/pull/11