This change adds the ES5 Object.seal 15.2.3.8 and Object.isSealed 15.2.3.11 methods.

Review URL: http://codereview.chromium.org/2993006

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@5072 ce2b1a6d-e550-0410-aec6-3dcde31c8c00