This includes:
- actually release handles kept by compilation info when compilation completes.
- do not use parallel recompilation on single core CPUs.
- artificially delay parallel recompilation for debugging.
- fix outdated assertions wrt optimization status.
- add "parallel" option to %OptimizeFunctionOnNextCall.

R=jkummerow@chromium.org
BUG=

Review URL: https://chromiumcodereview.appspot.com/12442002

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@13827 ce2b1a6d-e550-0410-aec6-3dcde31c8c00