Huge internal input lag (not related to video API)

[vanfanel]

Hi, Notaz!

The gpsp emulation core has an additional frame of internal input lag, compared to other GBA emulators.
It's NOT about emulation speed or video/audio APIs, you can see the details here:

libretro#42
As you can see, @Tatsuya79 has already shaved a frame, but still there's one additional frame of lag due to internals.
Maybe you could take a look? Thanks!