See associated bug: A continue if a do-while loop did jump back to the
loop header, instead of jumping to the condition.
This CL fixes this and adds a test case.

R=bradnelson@chromium.org, titzer@chromium.org
BUG=v8:5912

Review-Url: https://codereview.chromium.org/2693993002
Cr-Commit-Position: refs/heads/master@{#43178}