added signature constraint; replaced 'also' by '|>'; added  'sigclass' section; removed pure_syntax;
added signature constraint;
replaced 'also' by '|>';
added  'sigclass' section;
removed pure_syntax;

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