decide which mirror to choose locally and display result

closes #3904
port Tao.OpenAl to OpenTK.Audio.OpenAL
StyleCop
port Tao.OpenGl to OpenTK.Graphics.OpenGL and avoid Arb

closes #4540
only query for the extension we need
give a hint when someone forgot to install drivers on Windows
check for OpenGL version 2.0+
Merge pull request #4843 from Mailaender/local-mirrors

Moved mirror selection to the client
OpenRA.Thirdparty is now OpenRA.Support
Merge pull request #5273 from Mailaender/support-random-bitrot

OpenRA.Thirdparty is now OpenRA.Support
Merge pull request #5248 from Mailaender/sdl2-opentk

Ported Tao.OpenAL/OpenGL to SDL2/OpenTK