Add control dependencies to Projection and Int32Add/SubWithOverflow
operators, to prevent the scheduler from moving the Projection nodes
into the wrong place. This way the instruction selection can combine
the Int32Add/SubWithOverflow operations with the DeoptimizeIf and/or
DeoptimizeUnless nodes. This needs new operators CheckedInt32Add and
CheckedInt32Sub so that we can delay the actual lowering until the
effect/control linearizer.

This also makes CheckIf operator obsolete, so we can drop it.

R=jarin@chromium.org

Review-Url: https://codereview.chromium.org/2082993002
Cr-Commit-Position: refs/heads/master@{#37148}