Well, apparently, iOS 8.4 dispensed with the capability. Have to admit, I didn't notice, being busy with other toys at the time.
iOS 9 brought the capability back, but changed the way of accessing it somewhat.
First, make sure Home Sharing is turned on and that your OS X and iOS devices are on the same network.
Next, go to the Music app on your phone and touch the arrow next to Artists. You'll find Home Sharing in the resulting drop down menu. You can select your iTunes library from there, and either play the tunes on your phone, or plug the phone into a non-AirPlay amplifier. With an AirPlay amplifier you don't need your phone. You can just select AirPlay as your output device.
iOS 9 brought the capability back, but changed the way of accessing it somewhat.
First, make sure Home Sharing is turned on and that your OS X and iOS devices are on the same network.
Next, go to the Music app on your phone and touch the arrow next to Artists. You'll find Home Sharing in the resulting drop down menu. You can select your iTunes library from there, and either play the tunes on your phone, or plug the phone into a non-AirPlay amplifier. With an AirPlay amplifier you don't need your phone. You can just select AirPlay as your output device.