sibling. If sibling is NULL, then the row will be
prepended to the beginning of the list. iter will be changed to point to
this new row. The row will be empty after this function is called. To fill
in values, you need to call gtkListStoreSet or gtkListStoreSetValue.gtkListStoreInsertAfter(object, sibling)objectsiblingGtkTreeIter, or NULL. [ allow-none ]iterGtkTreeIter to set to the new row