Add missing links from GlobalPropertyCell to dependent_code

It produced orphan DependentCode nodes because links were not created explicitly in ExtractPropertyCellReferences and IndexedReferencesExtractor was disabled for ProperyCells.

R=danno@chromium.org, loislo@chromium.org

Review URL: https://codereview.chromium.org/19368002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@15694 ce2b1a6d-e550-0410-aec6-3dcde31c8c00