Handy and threaded video

[kivutar]

I'm not sure if it is a Handy bug, or a RetroArch bug. But it happens only with the handy core so far, so I will declare it here.

How to reproduce:

1. Use a menu like XMB
2. Enable threaded video
3. Launch handy with a game
4. Come back to the menu, it should not be locked to 60fps anymore

https://github.com/libretro/Lakka/issues/165