PPC: Add unoptimized/optimized variants of MathFloor TF code stub

PPC: Add unoptimized/optimized variants of MathFloor TF code stub

Port 8f13b655b8a10dae2116dd18b32f09337bb2d410

Original commit message:
    - 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.

R=danno@chromium.org, dstence@us.ibm.com, michael_dawson@ca.ibm.com
BUG=

Review URL: https://codereview.chromium.org/1207253003

Cr-Commit-Position: refs/heads/master@{#29542}