During computation of the side table, ignore stack effects of
instructions following any unconditional jump in the same block
(|unreachable|, |br|, |br_table| or |return| jump out of the block).
Without this fix, the current stack height might underflow, or we compute an
unnecessarily large max_stack_height_. Note that those instruction will
never get executed anyway.
Hence, we don't need to store any side table information for such
unreachable code.

R=rossberg@chromium.org
BUG=chromium:716936, chromium:715990

Change-Id: I282f7f18ba1b972a112210e692f6cd05cf32308c
Reviewed-on: https://chromium-review.googlesource.com/493266Reviewed-by: Andreas Rossberg <rossberg@chromium.org>
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#45059}