Port #3335 and #3373 from Citra: "Small SDL fixes" and "Print the actual error preventing SDL from working" (#637)

* Port #3335 and #3373 from Citra

* Fixup: Use the new logging placeholders

Given we utilize fmt, we don't need to provide our own functions for formatting anymore

video_core didn't even properly use them, and they were the source of
many otherwise-unnecessary dependencies from core to video_core.

Nightly builds now have "Citra Nightly" in the titlebar
Bleeding edge builds now have "Citra Bleeding Edge" in the titlebar

* Removes circular dependences (common should not depend on core)

Allows users to choose a single screen layout or a large screen layout.
Adds a configuration option to change the prominent screen.

This makes clang-format useful on those.

Also add a bunch of forgotten transitive includes, which otherwise
prevented compilation.

On SDL2 this allows it to use SDL_GL_GetProcAddress() instead of the
default function loader, and fixes a crash when using apitrace with an
EGL context.

On Qt we will need to migrate from QGLWidget to QOpenGLWidget and
QOpenGLContext before we can use gladLoadGLLoader() instead of
gladLoadGL(), since the former doesn’t expose a function loader.

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