Call FcFini to make memory debugging easier

FcFini frees all libary data structures so valgrind should report 0
allocations in use when the program exits.

fc-cache/fc-cache.c

@@ -457,6 +457,7 @@ main (int argc, char **argv)
      * library, and there aren't any signals flying around here.
      */
     FcConfigDestroy (config);
+    FcFini ();
     sleep (2);
     if (verbose)
 	printf ("%s: %s\n", argv[0], ret ? "failed" : "succeeded");