arrays maintenance
- fix of CoW; CopyOnWrite performed when PhpArray or its item is passed to a library function parameter marked as [PhpRw]
- OrderedDictionary._ensure_item_ref clenup; less array access, smaller code
- code maintenance; some usages of PhpException uses resources not hardcoded strings

git-tfs-id: [http://falcon:8080/tfs/Projects]$/Phalanger/Main;C4507