Don't fallback to the %StrictEqual / %Equal runtime functions for the
generic CompareIC slow path, but use the (new) StrictEqual and Equal
builtins instead. This avoids a performance cliff when mixing input
types for strict equality sites.

R=jochen@chromium.org
BUG=v8:4773

Review-Url: https://codereview.chromium.org/2609153002
Cr-Commit-Position: refs/heads/master@{#42021}