Make optimizations for debug configurable with compile flag.

To turn on optimizations for debug when building standalone, a compiler flag can be used:

make optdebug=on

R=jkummerow@chromium.org

Review URL: https://codereview.chromium.org/19164003

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@15678 ce2b1a6d-e550-0410-aec6-3dcde31c8c00