Remove incorrect use of ctype.h functions.

As far as I can tell the code should not change behaviour
depending on locale in any of these places.

Signed-off-by: Reimar Döffinger <Reimar.Doeffinger@gmx.de>

libavfilter/graphparser.c

@@ -20,7 +20,6 @@
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  */
 
-#include <ctype.h>
 #include <string.h>
 #include <stdio.h>