fixed compile warnings when using -Wall

further CHILD_SA rekeying work done:
	creation of a new CHILD_SA on a expire from a kernel works
	delete of old CHILD_SA still missing
	some issues when both initiate rekeing

src/charon/testing/kernel_interface_test.c

@@ -20,7 +20,8 @@
  * for more details.
  */
 
- 
+#include <unistd.h>
+
 #include "kernel_interface_test.h"
 
 #include <daemon.h>