Fixed the CDV_IsIPhone5() macro for iOS8 landscape

iOS8 introduces a change to screen orientation, making [UIScreen
bounds] orientation-dependent. Testing for the iPhone5 screen
resolution now needs to account for landscape (568x320) in addition to
portrait (320x568).

Details at
http://stackoverflow.com/questions/24150359/is-uiscreen-mainscreen-bound
s-size-becoming-orientation-dependent-in-ios8