Speedups vary depending on gcc version but never slower.

i7 mobile, Windows7-64

gcc 4.7.4
Results for 20 tests for each version:

            Base      Test      Diff
    Mean    1145602   1145932   -330
    StDev   26686     24296     4889

p-value: 0.527

gcc 4.8.2
Results for 20 tests for each version:

            Base      Test      Diff
    Mean    1118372   1136727   -18355
    StDev   11992     14562     3831

p-value: 1

gcc 4.9.2
Results for 20 tests for each version:

            Base      Test      Diff
    Mean    1089072   1091734   -2662
    StDev   11955     12205     2827

p-value: 0.827

No functional change.

…l-stockfish#211

official-stockfish#211