Add error message when the GDI Generic OpenGL renderer is encountered in Windows

This patch detects when Windows uses the "GDI Generic" software rasterizer for OpenGL rendering. This can happen when there are issues with the GPU drivers. This issue affects people with old Intel integrated GPUs. Apparently this can also happen with some AMD graphics cards when using drivers from Windows Update.

Instead of crashing when trying to use OpenGL commands unsupported by "GDI Generic", the game will show an error message and exit, possibly helping with troubleshooting efforts.