fix type of string constant length field in string table to Py_ssize_t (instead of long)
support surrogates in unicode string literals in Py3.3
clean up GetItemInt code and fix negative indexing of objects with length > max(Py_ssize_t)
clean up (Set|Del)ItemInt code and fix negative indexing of objects with length > max(Py_ssize_t)
fix ticket 636: build the correct slice objects on 2-value object slicing