Replace the malloc.h header with stdlib.h

--- src/ctl_curve.cpp.orig	Mon Nov  3 22:43:27 2014
+++ src/ctl_curve.cpp	Mon Nov  3 22:48:57 2014
@@ -20,8 +20,8 @@
  * Boston, MA 02111-1307, USA.
  */
 #include <calf/ctl_curve.h>
-#include <malloc.h>
 #include <stdint.h>
+#include <stdlib.h>
 #include <math.h>
 
 static gpointer parent_class = NULL;
