When removing debug_info from SharedFunctionInfo, clear all breakpoints associated with that debug_info.
This is needed because function will live in heap until next gc, and therefore can be found
by Runtime::FindSharedFunctionInfoInScript.

Review URL: http://codereview.chromium.org/2848032

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@4997 ce2b1a6d-e550-0410-aec6-3dcde31c8c00