This adds support for f64.min and f64.max, implemented on ia32, x64,
mips and mips64.

R=ahaas@chromium.org

Bug: v8:6600
Change-Id: Ib4383df08692c76df5861fe71a96c4354fdf10c1
Reviewed-on: https://chromium-review.googlesource.com/1028235
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Reviewed-by: Andreas Haas <ahaas@chromium.org>
Cr-Commit-Position: refs/heads/master@{#52838}