Some background: I wanted to test EGL backend on my old laptop with Intel graphics limited with OpenGL 2.1 / GLES 2.0. When trying to run any game this led to a crash with NULL GL_RENDERER, but not with GLX. Tracing has shown that wined3d tries to create a context with high `WGL_CONTEXT_MAJOR_VERSION_ARB`/`WGL_CONTEXT_MINOR_VERSION`, which is not supported by hardware, resulting in the creation of nil context in EGL, but due to lack of error handling it's always assumed to be successful. In GLX this results in an error and creating a context does not lead to success, after which it tries again to create a context with a lower `WGL_CONTEXT_MAJOR_VERSION_ARB` / `WGL_CONTEXT_MINOR_VERSION` until the actual context is created. Proper error handling when creating EGL context as in this patch also allows wined3d to work on such hardware.
-- v2: win32u: Handle errors when creating EGL context