New proof of gcd_zero after a change to Divides.ML made the old one fail
New proof of gcd_zero after a change to Divides.ML made the old one fail

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