removed cases_of;
renamed cases_tac to case_tac; tuned to work with basic HOL as well;
add_cases_induct: proper case names;
adapted to new PureThy.add_thms etc.;
Itrev = Main +
consts itrev :: 'a list => 'a list => 'a list
primrec
"itrev [] ys = ys"
"itrev (x#xs) ys = itrev xs (x#ys)"
end