Get rid of warnings when compiled with -Wformat-security

Change-Id: Ia671b74229001b02b2538a5d5f580532d7c88306
diff --git a/inc/config.h b/inc/config.h
index 2328d3a..fafa463 100644
--- a/inc/config.h
+++ b/inc/config.h
@@ -40,7 +40,7 @@
 		extern void stdimpl_print(const char *string);
 	#else
 		#include<stdio.h>
-		#define stdimpl_print printf
+		#define stdimpl_print(x) printf("%s", x)
 	#endif
 
 	#define ASSERT_STRING_BUFFER_MAX	64