[turbofan] Fix exit control flow in TryCatchBuilder.

[turbofan] Fix exit control flow in TryCatchBuilder.

This makes sure that the exit control flow that merges the try-block
with the catch-block after a try-catch-statement creates a new merge
node in cases where it has to. Otherwise dangling phi nodes might have
the wrong number of value inputs.

R=bmeurer@chromium.org
TEST=mjsunit/regress/regress-crbug-505354
BUG=chromium:505354
LOG=N

Committed: https://crrev.com/df06f1c71511ea7f60d0117111e3ee5346d47d83
Cr-Commit-Position: refs/heads/master@{#29362}

[Benedikt Meurer, 2015-06-30 03:00:34]

The CQ bit was checked by bmeurer@chromium.org

[Benedikt Meurer, 2015-06-30 03:00:35]

lgtm

[commit-bot: I haz the power, 2015-06-30 03:00:46]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1213183003/1

[commit-bot: I haz the power, 2015-06-30 03:23:35]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-06-30 03:23:50]

Patchset 1 (id:??) landed as
https://crrev.com/df06f1c71511ea7f60d0117111e3ee5346d47d83
Cr-Commit-Position: refs/heads/master@{#29362}