Kynurenine Hydroxylase Inhibitors Reduce Ischemic Brain Damage: Studies with (m-Nitrobenzoyl)-Alanine (mNBA) and 3,4-Dimethoxy-[-N-4-(Nitrophenyl)Thiazol-2YL]-Benzenesulfonamide (Ro 61-8048) in Models of Focal or Global Brain Ischemia