use stdlib.h instead of malloc.h

src/fscrawl.c

@@ -9,7 +9,7 @@
  */
 #include <unistd.h>
 #include <string.h>
-#include <malloc.h>
+#include <stdlib.h>
 #include <stdio.h>
 #include <errno.h>
 #include <dirent.h>

src/rbtree.c

@@ -10,7 +10,7 @@
  *   Based on the work of Julienne Walker's rbtree implementation
  *   http://www.eternallyconfuzzled.com/tuts/datastructures/jsw_tut_rbtree.aspx
  */
-#include <malloc.h>
+#include <stdlib.h>
 #include <string.h>
 #include "xalloc.h"
 #include "rbtree.h"