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 Sora no kiseki FC
Replace download frame in Sora no kiseki SC,and a comment for Sora no kiseki 3rd
Use E_FAIL instead of -1 and clean up
Merge pull request #6951 from chinhodado/patch-5

Use E_FAIL instead of -1 and clean up
d3d9: Show error when default shaders fail.
Add a .gitattributes to normalize newlines.

No code changes.
Offer to toggle graphics backends on any failure.

So, even if Direct3D 9 fails.
d3d9: Try harder to get a shader compile error.
Replace download frame in Boku no Natsuyasumi 2 and 4
Add a delay for creating fontlibs and fonts.

Matches tests, low bound on the delay.
Correct error codes in sceFontOpenUserMemory().
Process msgdialog abort on Update().

Matches tests.
Delay sceUtilityMsgDialogUpdate() per tests.

This is an approximate value, but it should be close.
Convert FormatMessage() to utf-8 to fix locale.

Otherwise we get non-utf-8 garbage if the user isn't in a Latin codepage.
Merge pull request #6955 from unknownbrackets/dialog-minor

Fix the utility/msgdialog/abort test