Implemented local load/store elimination on basic blocks.

Added mutex when accessing concurrent recompilation output queue. (Chromium issue 291236)

Don't lookup the cache for the result of Function::New. (Chromium issue 272579)

Tweaked HConstant::EmitAtUses() to eliminate useless constant generation. (Chromium issue 2881)

Performance and stability improvements on all platforms.

git-svn-id: http://v8.googlecode.com/svn/trunk@16781 ce2b1a6d-e550-0410-aec6-3dcde31c8c00