add a penalty for lambda-abstractions;
the penalty will kick in only when the goal contains no lambdas, in which case Sledgehammer previously totally disallowed any higher-order construct; this was too drastic;
lambdas are dangerous because they rapidly lead to unsound proofs; e.g. COMBI_def COMBS_def not_Cons_self2 with explicit_apply
(binary:application/x-msdos-program)