Uses the structure of an IEEE float to speed up
DoubleToUint32IfEqualToSelf, similar to FastD2UI. Micro-benchmarks show
a ~1.2x-2x speed-up, depending on the input.

Review-Url: https://codereview.chromium.org/2636453003
Cr-Commit-Position: refs/heads/master@{#42420}