This clears the currently pending message object whenever a try-block or
a finally-block is being entered in interpreted code. The intention is
to avoid memory leaks introduced by the message object. Also the message
object is being restored when a finally-block exits.

R=rmcilroy@chromium.org
TEST=cctest/test-heap/MessageObjectLeak
BUG=v8:4674
LOG=n

Review URL: https://codereview.chromium.org/1651993002

Cr-Commit-Position: refs/heads/master@{#33704}