xthm: added [[declaration]] syntax (abbreviates dummy_thm [att]);
xthm: added [[declaration]] syntax (abbreviates dummy_thm [att]);

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