Add config.h include to plistutil.c

tools/plistutil.c

diff --git a/tools/plistutil.c b/tools/plistutil.c
index d4bbbbe..dbbfbf6 100644
--- a/tools/plistutil.c
+++ b/tools/plistutil.c
@@ -20,6 +20,9 @@
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
  */
 
+#ifdef HAVE_CONFIG_H
+#include <config.h>
+#endif
 
 #include "plist/plist.h"