citra: Remove GLFW, Add SDL2

FindSDL2: Do not CACHE SDL2_* variables if library is not found

EmuWindow_SDL2: Set minimal client area at initialisation time

EmuWindow_SDL2: Corrections

EmuWindow_SDL2: Fix no decorations on startup on OS X

cmake: windows_copy_files

- Config: Add an option for selecting to use shader JIT or interpreter.
- Qt: Add a menu option for enabling/disabling the shader JIT.

The background color can be seen at the sides of the bottom screen or when the window is wider than normal.

Apparently inline comments is not necessarily standard in the INI format, and our parser was erroneously parsing the comments as values.

- Fixed NZCVT flags to properly save state when function returns.
- Fixed counter to keep track of the actual number of instructions executed.
- Fixed single-step mode to only execute one instruction at a time.
- DefaultIni: Removed comment that no longer applied to dyncom.

Before, it used to use whether the directory actually existed. As a result, .citra-emu/sdmc was never auto-created (something quite confusing to me until I read through the logs).

Uses QSettings on citra-qt, and inih on citra-cli.