Reset trunk to 3.28.71.1

git-svn-id: https://v8.googlecode.com/svn/trunk@23116 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Version 3.28.71.2 (merged r23115)

Revert 23058 - "Allow externalizing cons and sliced string."

TBR=yangguo@chromium.org

Review URL: https://codereview.chromium.org/473823002

git-svn-id: https://v8.googlecode.com/svn/trunk@23117 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Merge remote-tracking branch 'upstream/trunk' into trunk