Also lower JSToBoolean(x) where x is either some detectable receiver or
null, or any kind of receiver, null or undefined. Also fix a couple of
minor issues with the JSToBoolean lowering and tests.

R=yangguo@chromium.org
BUG=v8:5267

Review-Url: https://codereview.chromium.org/2530773002
Cr-Commit-Position: refs/heads/master@{#41241}