Detect and use SDL2 with help of this Dolphin CMake module:
https://github.com/dolphin-emu/dolphin/blob/master/CMakeTests/FindSDL2.cmake
Look for SDL_gamecontroller.h instead of SDL.h to prevent CMake from
using SDL1 include dirs
Update to SDL2
Update native submodule
Merge branch 'master' into sdl2

Conflicts:
	native
Replace download frame in Rezel Cross
Replace download frame in Toaru Majutsu to Kagaku no Ensemble
Another function replace in Kirameki School Life
Replace function in Hentai Ouji To Warawanai Neko
Replace function in Toradora! Portable
Update replace function for Toaru Majutsu to Kagaku no Ensemble.
D3D9 Get maxAnisotropyLevel from device caps
d3d9: Fix shader compile error X3014.
d3d9: Update some not-yet-used ps uniforms.
d3d9: Add stencil and blend replacement helpers.
d3d9: Disable color doubling without tex.

As the PSP does.
d3d9: Fix fbo tex clamp (usually shadows.)
d3d9: Replace alpha and premultiply blend.

Unfortunately they are fairly tied together.
d3d9: Add BindFramebufferColor().
d3d9: Specify tex stage for binding framebuf color.