This introduces iterators for the parameters and return types of a
signature. This required extending the constructor of iterator_range
for perfect forwarding.

I also moved the HasJSCompatibleSignature to a header file in order to
reuse it from the interpreter.

R=ahaas@chromium.org, titzer@chromium.org

Change-Id: Ie77f87ef87fdfd3138b2106640ac7c481cf247e6
Reviewed-on: https://chromium-review.googlesource.com/455777
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Reviewed-by: Andreas Haas <ahaas@chromium.org>
Reviewed-by: Ben Titzer <titzer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#43854}