Do not implicitly convert non-object receivers for strict mode functions.

This was still the case for Array.prototype.* builtin functions.

R=rossberg@chromium.org
BUG=v8:2273

Review URL: https://chromiumcodereview.appspot.com/13473009

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@14149 ce2b1a6d-e550-0410-aec6-3dcde31c8c00