GEN_VALIDATE : bool -> tactic -> tactic
Suppose tac applied to the goal (asl,g) produces a justification that creates a theorem A |- g'. Then GEN_VALIDATE false adds new subgoals for members of A, regardless of whether they are present in asl.
Also fails if tac fails when applied to the given goal.
1 subgoal: val it = r ------------------------------------ 0. p 1. q > e (VALIDATE (ACCEPT_TAC uthr')) ; OK.. 1 subgoal: val it = p' ------------------------------------ p : proof
> e (GEN_VALIDATE false (ACCEPT_TAC uthr')) ; OK.. 2 subgoals: val it = q ------------------------------------ 0. p 1. q p' ------------------------------------ 0. p 1. q