D3D8: Fix missing prototypes when using nVidia OpenGL headers

[H. Verbeet]

Changelog:
 - Fix missing prototypes when using nVidia OpenGL headers

Index: dlls/d3d8/d3d8_private.h
===================================================================
RCS file: /home/wine/wine/dlls/d3d8/d3d8_private.h,v
retrieving revision 1.66
diff -u -r1.66 d3d8_private.h
--- dlls/d3d8/d3d8_private.h	11 Jul 2005 13:21:17 -0000	1.66
+++ dlls/d3d8/d3d8_private.h	27 Sep 2005 23:22:34 -0000
@@ -29,6 +29,7 @@

 /* THIS FILE MUST NOT CONTAIN X11 or MESA DEFINES */
 #define XMD_H /* This is to prevent the Xmd.h inclusion bug :-/ */
+#define GL_GLEXT_PROTOTYPES
 #include <GL/gl.h>
 #define GLX_GLXEXT_PROTOTYPES
 #include <GL/glx.h>