Fixed the CDV_IsIPhone5() macro for iOS8 landscape

iOS8 introduces a change to screen orientation, making [UIScreen bounds] orientation-dependent. As a result, testing if the screen resolution matches the iPhone5, as this macro does, now needs to account for landscape (568x320) in addition to portrait (320x568).

Details at http://stackoverflow.com/questions/24150359/is-uiscreen-mainscreen-bounds-size-becoming-orientation-dependent-in-ios8