- Add a TurboFanIC class, derived from TurboFanCodeStub, that
  automatically distinguishes between versions of the IC called from
  optimized and unoptimized code.
- Add appropriate InterfaceDescriptors for both the versions of the
  stub called from unoptimized and optimized code
- Change the MathFloor TF stub generator to output either the
  for-optimized or for-unoptimized version based on the minor_key
  parameter.

Review URL: https://codereview.chromium.org/1225943002

Cr-Commit-Position: refs/heads/master@{#29534}