is both on top of the stack and also in r0.  This makes
sense because the receiver is usually in r0 anyway.  We may
remove it from the stack later.  Also removes some spilled
scopes from the code generator allowing it to keep expression
temporaries in registers more.
Review URL: http://codereview.chromium.org/1751019

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@4518 ce2b1a6d-e550-0410-aec6-3dcde31c8c00