Support stepping in functions called using CallFunction stub. When Debug::PrepareStep is called to prepare 'step in' and current code target is CallFunction stub, the debugger will find function being called on the expression stack and flood it with one shot breakpoints.

BreakLocationIterator changed to treat 'debugger;' statements as a possible break location. Since 'debugger;' statement should always invoke debugger it is hanled in a special way.

Related Chromium issue:
http://code.google.com/p/chromium/issues/detail?id=17978
Review URL: http://codereview.chromium.org/195015

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@2830 ce2b1a6d-e550-0410-aec6-3dcde31c8c00