Add support for retrieving i64 parameters and returning them from a
liftoff function.

R=ahaas@chromium.org

Bug: v8:6600
Change-Id: I407b6e3cde6967bacc59d8c3a54e0d5798164d18
Reviewed-on: https://chromium-review.googlesource.com/909215
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Reviewed-by: Andreas Haas <ahaas@chromium.org>
Cr-Commit-Position: refs/heads/master@{#51214}