Needs ctype.h

Index: lib/lowten.c
--- lib/lowten.c.orig
+++ lib/lowten.c
@@ -17,6 +17,7 @@
  * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  */
 
+#include <ctype.h>
 #include "cim.h"
 
 /******************************************************************************
