Detect the presence of the I830 fb driver rather than 
just assuming it always exists.

--- DirectFB-0.9.22/configure
+++ DirectFB-0.9.22/configure
@@ -23622,9 +23622,9 @@
 /* end confdefs.h.  */
 
 #include <linux/fb.h>
-//#ifdef FB_ACCEL_I830
+#ifdef FB_ACCEL_I830
   yes
-//#endif
+#endif
 
 _ACEOF
 if (eval "$ac_cpp conftest.$ac_ext") 2>&5 |