Refactor SDL device to use the same abstraction as other devices

In particular this makes the OpenGL procedure stuff work.
fixes https://github.com/minetest/minetest/issues/12265

source/Irrlicht/CMakeLists.txt

@@ -188,6 +188,7 @@ set(IRRDRVROBJ
 	CGLXManager.cpp
 	CWGLManager.cpp
 	CEGLManager.cpp
+	CSDLManager.cpp
 	mt_opengl_loader.cpp
 )