Move all system calling parts of the libs in a separate library.

[aconstlink]

The graphics layer contains the implementation of the renderer which use D3D, OpenGL and OpenGLes in the backends. The application layer also uses D3D11, WGL, GLX and EGL to create a rendering window for use by the backends. Due the the fact that CMake is used and the graphics targets are simply linked to the layers, there is not a particular effort elsewhere in the engine to include those libs.

The idea would be to move all the system calling parts of the engine in one single layer like a platform layer. So the other layers requiring the platform specifics can easily be linked to the platform lib which implements the required interfaces.

Libs that require attention:

• application lib: d3d, wgl, win32, egl, xlib
• device lib: xinput, raw input, xlib
• audio lib: wasapi, xaudio, oal?
• graphics lib: d3d, gl, gles

[aconstlink]

This ticket is ongoing and may not be required anymore because everything will be put in the platform lib anyway.