BNF/Examples/Stream: rename same to sconst; define same, fromN in terms of siterate
BNF/Examples/Stream: rename same to sconst; define same, fromN in terms of siterate

MerelyAPseudonym/isabelle,MerelyAPseudonym/isabelle,MerelyAPseudonym/isabelle,MerelyAPseudonym/isabelle,MerelyAPseudonym/isabelle,MerelyAPseudonym/isabelle