Contribution of PowerPC port (continuation of 422063005 and 817143002). This patch covers
the key changes needed to the common files needed to support AIX. Subsequent
patches will cover:
- changes to update the ppc directories so they are current with the changes
in the rest of the project.
- remaining AIX changes not resolved by 4.8 compiler
- individual optimizations for PPC

This is based off of the GitHub repository
https://github.com/andrewlow/v8ppc

R=danno@chromium.org, svenpanne@chromium.org
BUG=

Review URL: https://codereview.chromium.org/866843003

Cr-Commit-Position: refs/heads/master@{#26343}