Special case the ConstantPoolArray in MarkCompactCollector::MigrateObject since it could contain
integer value entires which look like tagged pointers.

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

Review URL: https://codereview.chromium.org/304223002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@21934 ce2b1a6d-e550-0410-aec6-3dcde31c8c00