Compare JSObjects by identity immediately.

When invoking EQUALS JS builtin, 1st argument is passed as a receiver and
if it's a global object, it gets overwritten with global proxy object and
thus one gets incorrect results.

BUG=v8:1082

TBR=ricow@chromium.org

Review URL: http://codereview.chromium.org/6461028

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@6708 ce2b1a6d-e550-0410-aec6-3dcde31c8c00