Rollback of r13728 in 3.17 branch.

Make __proto__ a foreign callback on Object.prototype.

R=danno@chromium.org,rossberg@chromium.org
BUG=v8:621,v8:1949,v8:2441
TEST=mjsunit,cctest,test262

Review URL: https://codereview.chromium.org/14200035

git-svn-id: https://v8.googlecode.com/svn/branches/3.17@14313 ce2b1a6d-e550-0410-aec6-3dcde31c8c00