Missing includes for FreeBSD.

Change-Id: I4ea02a41ed614047ecda156d0c572b04baa174e6
Reviewed-on: https://boringssl-review.googlesource.com/1852
Reviewed-by: Adam Langley <agl@google.com>
diff --git a/ssl/test/test_config.cc b/ssl/test/test_config.cc
index 70543cc..270fbfb 100644
--- a/ssl/test/test_config.cc
+++ b/ssl/test/test_config.cc
@@ -14,6 +14,7 @@
 
 #include "test_config.h"
 
+#include <stdio.h>
 #include <string.h>
 
 #include <memory>