For now use 4x anti-aliasing by default, it's quite a bit faster than x8 and I can barely tell the difference

git-svn-id: svn+ssh://svn.code.sf.net/p/supertuxkart/code/main/trunk@10340 178a84e3-b1eb-0310-8ba1-8eac791a3b58

src/graphics/irr_driver.cpp

@@ -191,7 +191,7 @@ void IrrDriver::initDevice()
                     core::dimension2du(UserConfigParams::m_width,
                                        UserConfigParams::m_height);
                 if (UserConfigParams::m_fullscreen_antialiasing)
-                    params.AntiAlias = 8;
+                    params.AntiAlias = 4;
             
                 m_device = createDeviceEx(params);