The new operator provides a second output which indicates whether the
conversion from float64 to int64 was successful or not. The second
output returns 0 if the conversion fails. If the conversion succeeds,
then the second output is differs from 0.

The second output can be ignored, which means that the operator can be
used the same way as the original operator.

I implemented the new operator on x64 and arm64. @v8-mips-ports and
@v8-ppc-ports, can you please take care of the mips64 and ppc64
implementation of the second output?

R=titzer@chromium.org, v8-arm-ports@googlegroups.com

Review URL: https://codereview.chromium.org/1495213003

Cr-Commit-Position: refs/heads/master@{#32653}