Fixed compilation on platforms using SDL window management(?)

doomsday/engine/portable/src/sys_opengl.c

@@ -3,8 +3,8 @@
  * License: GPL
  * Online License Link: http://www.gnu.org/licenses/gpl.html
  *
- *\author Copyright © 2003-2009 Jaakko Keränen <jaakko.keranen@iki.fi>
- *\author Copyright © 2007-2009 Daniel Swanson <danij@dengine.net>
+ *\author Copyright © 2003-2010 Jaakko Keränen <jaakko.keranen@iki.fi>
+ *\author Copyright © 2007-2010 Daniel Swanson <danij@dengine.net>
  *\author Copyright © 2006 Jamie Jones <yagisan@dengine.net>
  *
  * This program is free software; you can redistribute it and/or modify
@@ -56,11 +56,11 @@
 gl_state_t GL_state;
 gl_state_ext_t GL_state_ext;
 
-#ifdef GL_EXT_framebuffer_object
+#ifdef WIN32
+# ifdef GL_EXT_framebuffer_object
 PFNGLGENERATEMIPMAPEXTPROC glGenerateMipmapEXT;
-#endif
+# endif
 
-#ifdef WIN32
 PFNWGLSWAPINTERVALEXTPROC wglSwapIntervalEXT;
 PFNWGLCHOOSEPIXELFORMATARBPROC wglChoosePixelFormatARB;