refine blocked levitation/flight (trunk only)

Levitation side-effects get skipped if Levitation toggles while it
is blocked, so BFlying (the reason Flying is blocked) could become stale
in some situations.  Enlightment feedback about latent flight capability
was the only thing affected.

src/potion.c

@@ -934,6 +934,7 @@ peffects(otmp)
 		} else
 		    incr_itimeout(&HLevitation, rn1(140,10));
 		if (Levitation) spoteffects(FALSE);	/* for sinks */
+		float_vs_flight();
 		break;
 	case POT_GAIN_ENERGY:			/* M. Stephenson */
 		{	register int num;