Allow quake to compile with -Wformat-security

Change-Id: Ia37a1dbf5f6bf80082792f6f827376b9ef844349
diff --git a/quake/src/WinQuake/sv_main.cpp b/quake/src/WinQuake/sv_main.cpp
index 3845d30..f9eb24e 100644
--- a/quake/src/WinQuake/sv_main.cpp
+++ b/quake/src/WinQuake/sv_main.cpp
@@ -204,7 +204,7 @@
 	else
 		MSG_WriteByte (&client->message, GAME_COOP);
 
-	sprintf (message, pr_strings+sv.edicts->u.v.message);
+	sprintf (message, "%s", pr_strings+sv.edicts->u.v.message);
 
 	MSG_WriteString (&client->message,message);