IDs for PlayStation 4 controllers
NOTES
WINDOWS: seems to work fine without any special drivers on Windows 10 (and I seem to recall the same on Windows 7). DS4Windows is the popular 3rd-party utility here, but it will make the PS4 controller look like a 360 controller, which means that it will be indistinguishable from an XInput device to flixel (DS4Windows: http://ds4windows.com).
LINUX: the PS4 controller will be detected as an XInput device when using xpad (see notes in XInputID.hx)
MAC: the PS4 controller seemed to work perfectly without anything special installed, and was not detected in the 360Controller control panel, so it might just work right out of the box!