Implemented ES5-conformant semantics for inherited setters and read-only properties. Currently behind --es5_readonly flag, because it breaks WebKit bindings.

Exposed last seen heap object id via v8 public api.

Performance and stability improvements on all platforms.

git-svn-id: http://v8.googlecode.com/svn/trunk@11724 ce2b1a6d-e550-0410-aec6-3dcde31c8c00