Fix compilation of OpenGL driver with OpenGL disabled.

git-svn-id: svn://svn.code.sf.net/p/irrlicht/code/trunk@2520 dfc29bdd-3216-0410-991c-e03cc46cb475

source/Irrlicht/COpenGLDriver.h

@@ -9,6 +9,14 @@
 
 #include "SIrrCreationParameters.h"
 
+namespace irr
+{
+	class CIrrDeviceWin32;
+	class CIrrDeviceLinux;
+	class CIrrDeviceSDL;
+	class CIrrDeviceMacOSX;
+}
+
 #ifdef _IRR_COMPILE_WITH_OPENGL_
 
 #include "CNullDriver.h"
@@ -17,11 +25,7 @@
 #include "COpenGLExtensionHandler.h"
 
 namespace irr
-{
-	class CIrrDeviceWin32;
-	class CIrrDeviceLinux;
-	class CIrrDeviceSDL;
-	class CIrrDeviceMacOSX;
+{
 
 namespace video
 {