AirPlay, Apple’s revamped version of AirTunes meant for streaming audio, video, and photos to compatible devices, may also allow for streaming of content from third-party applications, according to a new report. Citing testing done by a reader using the first iOS 4.2 beta, Mac Rumors reports that every application that uses the standard iOS audio/video playback interface now shows an AirPlay button for streaming. While the second-generation…