Stack trace API: poison stack frames below the first strict mode frame. (issue 2564)

Made Isolate::GetHeapStatistics robust against half-initialized isolates (Chromium issue 2591).

Finished implementation of ES6 symbols aka. private names (issue 2158).

Performance and stability improvements on all platforms.

git-svn-id: http://v8.googlecode.com/svn/trunk@14137 ce2b1a6d-e550-0410-aec6-3dcde31c8c00