restorer: Add sys/resource.h header

Otherwise PRIO_PROCESS may be not found.
Reported-by: Andrew Grigorev <andrew@ei-grad.ru>
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

restorer.c

@@ -11,6 +11,7 @@
 #include <fcntl.h>
 #include <unistd.h>
 #include <sched.h>
+#include <sys/resource.h>
 
 #include "compiler.h"
 #include "types.h"