SSE: force the stack to 16-byte alignment everywhere.

This fixes gh-52.

--HG--
extra : rebase_source : b503958047fd9a91d87068f611ea9fb93c60178f
Drop some trailing whitespace that crept in

--HG--
extra : rebase_source : b58566d6984d7c66e66aaebfee571ae677019739