Prevent direct inclusion of headers from TF.

R=jochen@chromium.org, titzer@chromium.org

Review URL: https://codereview.chromium.org/438243004

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@22874 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Enable C++11. Synch toolchains with Chrome.

* Consistently enable C++11 features on all platforms.
* Use the same ARM toolchain version as Chrome.
* Make clang the default on Mac OS X, just like Chrome.
* Use C99 on Mac OS X, again following Chrome.
* Small build fixes.

R=bmeurer@chromium.org

Review URL: https://codereview.chromium.org/440663002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@22875 ce2b1a6d-e550-0410-aec6-3dcde31c8c00