Bugfix/trac10510

See https://svn.boost.org/trac/boost/ticket/10510

This fixes a bug in the SIMD optimization of operator<.
According to the documentation on https://software.intel.com/sites/landingpage/IntrinsicsGuide/ it is safe to assume that  `_mm_movemask_epi8` will set the 16 most significant bits of the return value to 0: `dst[MAX:16] := 0`

uint32_t is required in the final compare to handle `0x0000FFFF < 0xFFFFFFFF` (the results of the `(x - 1) ^ x` trick)