This introduces a new {JumpLoop} bytecode to combine the OSR polling
mechanism modeled by {OsrPoll} with the actual {Jump} performing the
backwards branch. This reduces the overall size and also avoids one
additional dispatch. It also makes sure that OSR polling is only done
within real loops.

R=rmcilroy@chromium.org
BUG=v8:4764

Review-Url: https://codereview.chromium.org/2331033002
Cr-Commit-Position: refs/heads/master@{#39384}