Compare the whole word on 64-bit architectures with the kHoleNanInt64 value
since comparing only upper part produces slightly worse code on x64.
Currently TurboFan is not able to fold (array + ((const1 + index*scale) + const))
into single addressing mode: (array + (const + index*scale)).

BUG=chromium:645414

Review-Url: https://codereview.chromium.org/2322283002
Cr-Commit-Position: refs/heads/master@{#39335}