These guards are useless anyways once you make it throw the
effect/control linearizer because all memory operations and
calls are connected to the control and/or effect chain anyways
afterwards.

Drive-by-fix: Fail in the InstructionSelector if we ever see
a Guard node.

R=jarin@chromium.org
BUG=chromium:612142

Review-Url: https://codereview.chromium.org/1980383002
Cr-Commit-Position: refs/heads/master@{#36302}