Replace use of deprecated C Standard library headers in C++ code.

Change-Id: I9fa6630c7e4bdb2897df34d417635d8c7d8253bc
Signed-off-by: Tyler Chatow <tchatow@gmail.com>
diff --git a/frc971/control_loops/control_loop.h b/frc971/control_loops/control_loop.h
index 741b32f..80b0bca 100644
--- a/frc971/control_loops/control_loop.h
+++ b/frc971/control_loops/control_loop.h
@@ -1,9 +1,8 @@
 #ifndef AOS_CONTROL_LOOP_CONTROL_LOOP_H_
 #define AOS_CONTROL_LOOP_CONTROL_LOOP_H_
 
-#include <string.h>
-
 #include <atomic>
+#include <cstring>
 
 #include "aos/events/event_loop.h"
 #include "aos/time/time.h"