Adds the ability to show some warning messages in the Display settings, and also make ANGLE the default renderer with Intel graphics drivers. This only affects Windows.

This is a bit like D8459, but implemented a bit differently.

The messages I wrote aren't very intuitive. The UI and styles probably also need a bit of polish.

Available warning messages:

• "The graphics driver in use does not meet the OpenGL requirements." -- native OpenGL doesn't meet required OpenGL 2.1 / OpenGL 3 with deprecated features support. (No warning for when ANGLE is not usable, which is not likely to happen.)
• "The graphics driver in use may not work well with OpenGL." -- native OpenGL is available but Qt's internal detection favours ANGLE over native OpenGL.
• "ANGLE is using a software Direct3D renderer, which is not hardware-accelerated and may be very slow. This can happen if the graphics drivers are not properly installed, or when using a Remote Desktop session." -- ANGLE Direct3D is using the fallback software renderer for whatever reasons.
• "The Intel graphics driver in use is known to have issues with OpenGL." -- known broken Intel OpenGL drivers that is not already blacklisted by Qt
• "Intel graphics drivers tend to have issues with OpenGL so ANGLE will be used by default. You may manually switch to OpenGL but it is not guaranteed to work properly." -- any other Intel OpenGL drivers that isn't already known to be buggy, including those which are known to very likely work fine.

Screenshot: