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.;
Fib = WF_Rel +
consts fib :: nat => nat
recdef fib "measure(%n. n)"
"fib 0 = 0"
"fib 1 = 1"
"fib (Suc(Suc x)) = fib x + fib (Suc x)"
end