Contribution of PowerPC port (continuation of 422063005). The inital patch
covers the core changes to the common files.  Subsequent patches will cover
changes to common files to support AIX and to update the ppc directories so
they are current with the changes in the rest of the project.

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

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

Review URL: https://codereview.chromium.org/817143002

Cr-Commit-Position: refs/heads/master@{#26091}