glx: Compile dri2.c only if GLX_DIRECT_RENDERING is defined.

src/glx/x11/dri2.c

@@ -31,6 +31,8 @@
  */
 
 
+#ifdef GLX_DIRECT_RENDERING
+
 #define NEED_REPLIES
 #include <X11/Xlibint.h>
 #include <X11/extensions/Xext.h>
@@ -377,3 +379,5 @@ DRI2CopyRegion(Display * dpy, XID drawable, XserverRegion region,
    UnlockDisplay(dpy);
    SyncHandle();
 }
+
+#endif /* GLX_DIRECT_RENDERING */