Fix compilation on OS X 10.9
Make SSE code work with unaligned memory.

SSE code is 43% faster than C code on 16-bytes aligned memory
SSE code is 29% faster than C code on unaligned memory
On a Core 2 duo, the unaligned compatible SSE code is 4.4% slower than aligned-required SSE code with aligned memory
On Nehalem processors and newer, there's no speed disadvantage in using unaligned move SSE instructions vs aligned move SSE instructions.