"Own" symbols are symbols that can only denote own properties of
objects.

R=hpayer@chromium.org, verwaest@chromium.org

Committed: https://code.google.com/p/v8/source/detail?r=23056

Review URL: https://codereview.chromium.org/464473002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@23083 ce2b1a6d-e550-0410-aec6-3dcde31c8c00