[janitorial] dlls/opengl32 -Write-strings cleanup

[MichaelGuennewig@gmx.de (Michael Günnewig)]

Fixed warnings with gcc option "-Wwrite-strings".

--- dlls/opengl32/opengl_ext.h.~1.4.~	2002-09-25 02:29:57.000000000 +0200
+++ dlls/opengl32/opengl_ext.h	2003-10-03 13:07:57.000000000 +0200
@@ -51,8 +51,8 @@
 
 
 typedef struct {
-  char  *name;     /* name of the extension */
-  char  *glx_name; /* name used on Unix's libGL */
+  const char  *name;     /* name of the extension */
+  const char  *glx_name; /* name used on Unix's libGL */
   void  *func;     /* pointer to the Wine function for this extension */
   void **func_ptr; /* where to store the value of glXGetProcAddressARB */
 } OpenGL_extension;