This operator now provides a second output which indicates whether the
conversion from float32 to int64 was successful or not. The second output
returns 0 if the conversion fails, or something else if the conversion succeeds.

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

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

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

Review URL: https://codereview.chromium.org/1504363002

Cr-Commit-Position: refs/heads/master@{#32737}