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/aos/starter/starter_test.cc b/aos/starter/starter_test.cc
index fafeb77..dea27e9 100644
--- a/aos/starter/starter_test.cc
+++ b/aos/starter/starter_test.cc
@@ -1,5 +1,4 @@
-#include <signal.h>
-
+#include <csignal>
 #include <future>
 #include <thread>