As reported, you'd get the "float gently to the ground" message even while
riding a flying steed. Rearranged the code and added a new case for this.
I found it odd that Hallucination protected you from falling out of the
saddle due to the Sokoban air currents. The message implied otherwise, so
I've made the sokoban_trap code apply in both cases.
c40d876c3b