Can't include <stddef.h> when building XFree86 server - define

ptrdiff_t to int instead

include/GL/gl.h

@@ -38,7 +38,11 @@
  */
 #if !defined(__SCITECH_SNAP__)
 
+#ifndef XFree86Server
 #include <stddef.h>     /* to get ptrdiff_t, used below */
+#else
+#define ptrdiff_t int
+#endif
 
 #if defined(__BEOS__)
 #include <stdlib.h>     /* to get some BeOS-isms */

include/GL/glext.h

@@ -3290,7 +3290,11 @@ typedef GLboolean (APIENTRYP PFNGLISPROGRAMARBPROC) (GLuint program);
 #define GL_ARB_vertex_buffer_object 1
 /* GL types for handling large vertex buffer objects */
 /* Only used by this extension for now; later needs to be moved earlier in glext.h */
+#ifndef XFree86Server
 #include <stddef.h>
+#else
+#define ptrdiff_t int
+#endif
 typedef ptrdiff_t GLintptrARB;
 typedef ptrdiff_t GLsizeiptrARB;
 #ifdef GL_GLEXT_PROTOTYPES