[turbofan] Respect effect input when lowering JSToBoolean for string inputs.

[turbofan] Respect effect input when lowering JSToBoolean for string inputs.

This allows us to re-enable the mjsunit/tools/profile test case.

R=jarin@chromium.org
BUG=v8:4493
LOG=n

Committed: https://crrev.com/2abd768e873d4e7c53687b8a6707c8b1d1966589
Cr-Commit-Position: refs/heads/master@{#31416}

[Jarin, 2015-10-20 14:54:25]

lgtm

[Benedikt Meurer, 2015-10-20 15:04:46]

The CQ bit was checked by bmeurer@chromium.org

[commit-bot: I haz the power, 2015-10-20 15:04:57]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1418643002/20001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1418643002/20001

[commit-bot: I haz the power, 2015-10-20 15:24:23]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2015-10-20 15:24:47]

Patchset 2 (id:??) landed as
https://crrev.com/2abd768e873d4e7c53687b8a6707c8b1d1966589
Cr-Commit-Position: refs/heads/master@{#31416}

[Michael Achenbach, 2016-02-04 10:31:39]

machenbach@chromium.org changed reviewers:
+ machenbach@chromium.org

[Michael Achenbach, 2016-02-04 10:31:39]

Seeing a bunch of turbo crashes for tools/profile lately:
https://build.chromium.org/p/client.v8/builders/V8%20Win32/builds/412/steps/C...
https://build.chromium.org/p/client.v8/builders/V8%20Mac64%20ASAN/builds/4406...