Apple is currently testing two prototype iPhones, claims Jefferies analyst Peter Misek. One of these is said to be Apple’s next flagship model, nicknamed the iPhone 5S. The nature of the other phone is unclear, but could possibly be the rumored low-end iPhone. In any case Misek expects the 5S to be an incremental upgrade over the 5, and debut in June or July, even though the 5 and 4S were both fall releases….