If an exception is thrown and the wasm interpreter entry frame is
unwound, also the internal frames in the interpreter need to be unwound.
We did not do so before, leaving a corrupted internal state of the wasm
interpreter. Thus reusing it would fail.
This CL fixes this and adds a test which reenters a previously unwound
wasm interpreter. It checks that this works and the correct stack is
returned.
This test also requires support for calling an imported function which
throws, so this change is also included here.

R=ahaas@chromium.org, titzer@chromium.org
BUG=v8:5822

Change-Id: I12fb843f7a371a4e618b4ac63ed3299667a03a82
Reviewed-on: https://chromium-review.googlesource.com/453938
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Reviewed-by: Andreas Haas <ahaas@chromium.org>
Cr-Commit-Position: refs/heads/master@{#43937}