Do not allow external strings in old pointer space.

R=mstarzinger@chromium.org
BUG=

Review URL: https://codereview.chromium.org/20723002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@15906 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Disable mjsunit test when parallel recompilation is not available.

R=yangguo@chromium.org

Review URL: https://codereview.chromium.org/20573003

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@15907 ce2b1a6d-e550-0410-aec6-3dcde31c8c00