Record the function return position as the end of the function source. Don't record function entry and return positions as statement positions.

Added a test for source position for break at function return.
Review URL: http://codereview.chromium.org/67109

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@1706 ce2b1a6d-e550-0410-aec6-3dcde31c8c00