Port 97161a29

Original commit message:
    TryTruncateFloat32ToUint64 converts a float32 to a uint64. Additionally it
    provides an optional second return value which indicates whether the conversion
    succeeded (i.e. float32 value was within uint64 range) or not.

    Additionally I fixed a bug on x64 and mips64 in the implementation of
    TryTruncateFloat64ToUint64. Cases where the input value was between -1 and 0
    were handled incorrectly.

R=ahaas@chromium.org, joransiu@ca.ibm.com, jyan@ca.ibm.com, michael_dawson@ca.ibm.com
BUG=

Review URL: https://codereview.chromium.org/1533613002

Cr-Commit-Position: refs/heads/master@{#32919}