doc-src/Tutorial/Misc/InfixTree.ML

added invent_type_names;
added add_tvarsT etc. (from drule.ML);

Goal "!xs. linInfixList t xs = infixList t @ xs";
by(induct_tac "t" 1);
by(Simp_tac 1);
by(Asm_simp_tac 1);