Linux compatibility + little performance tuning (SSE4.2)

These commits make the tests Linux-compatible, and slightly improve performance:

Performance on Core i3-3217U (Ivy Bridge), before performance tuning:
SIMD rANS: 435626 bytes
5156840 clocks, 6.7 clocks/symbol (255.6MB/s)
5145488 clocks, 6.7 clocks/symbol (256.1MB/s)
5136676 clocks, 6.7 clocks/symbol (256.6MB/s)
5144460 clocks, 6.7 clocks/symbol (256.2MB/s)
5145168 clocks, 6.7 clocks/symbol (256.1MB/s)
decode ok!

Performance after tuning:
SIMD rANS: 435626 bytes
5103428 clocks, 6.6 clocks/symbol (258.2MB/s)
5090396 clocks, 6.6 clocks/symbol (258.9MB/s)
5087912 clocks, 6.6 clocks/symbol (259.0MB/s)
5086376 clocks, 6.6 clocks/symbol (259.1MB/s)
5088496 clocks, 6.6 clocks/symbol (259.0MB/s)
decode ok!