Test result more reproducible

git-svn-id: https://yquem.inria.fr/compcert/svn/compcert/trunk@1201 fca1b0fc-160b-0410-b1d3-a4f43f01ea2e

test/c/Results/fft

-262144 points, error 3.20142e-10
+262144 points, result OK

test/c/fft.c

@@ -186,6 +186,6 @@ int main(int argc, char ** argv)
   }
   zm = zr;
   if (zr < zi) zm = zi;
-  printf("%d points, error %g\n", np, zm);
+  printf("%d points, %s\n", np, zm < 1e-9 ? "result OK" : "WRONG result");
   return 0;
 }