[Simulator] Keep touch-event coords. within valid range

Currently coords. received during touch events can be negative/greater than the devices screen size, I think to prevent any “gotcha’s” or the requirement of special-case coding for the developer, Corona/The Simulator should clamp touch coords. to the devices physical screen size (ie 320x480). [import]uid: 1581 topic_id: 195 reply_id: 300195[/import]