added METHOD_CASES, resolveq_cases_tac;
removed multi_resolveq;
improved 'tactic' method: bind thm(s) function;
Sep2 = List +
consts sep :: "'a * 'a list => 'a list"
recdef sep "measure (%(a,xs). length xs)"
"sep(a, x#y#zs) = x # a # sep(a,y#zs)"
"sep(a, xs) = xs"
end