Revert "Revert commits"

This reverts commit f7318fce623508d8b014b43f48de3f8d4bf47f39.
Revert "Revert "GCC 4.7 O3 and aliasing Optimizations""

This reverts commit 34a330d719eb7176bd18743f81cd44bb1e22e38a.
Revert "Revert "Use GCC 4.7 from google""

This reverts commit 683679e3cb73fbf2c9352907b7001a5ad3149a13.