This adds a bigint branch to the typed-optimization of the TypeOf
bytecode. The implementation of the TestTypeOf bytecode already supports
bigints, as does the Typeof stub.

R=jarin@chromium.org

Bug: v8:6791
Change-Id: Ib9a21f3fc48d57873b014a01c68a143bfb8ac6c6
Reviewed-on: https://chromium-review.googlesource.com/778880
Commit-Queue: Georg Neis <neis@chromium.org>
Reviewed-by: Jaroslav Sevcik <jarin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#49509}