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
This commit:
* Adds a new subproject, audio_core.
* Defines structures that exist in DSP shared memory.
* Hooks up various other parts of the emulator into audio core.
This sets the foundation for a later HLE DSP implementation.
Several cleanups to the buildsystem:
- Do better factoring of common libs between platforms.
- Add support to building on Windows.
- Remove Qt4 support.
- Re-sort file lists and add missing headers.
