Use the C++11 random number generator instead of rand().

This is safer, faster, and doesn't require seeding.

modules/dns.cpp

@@ -679,7 +679,7 @@ public:
 		: Manager(creator)
 		, Timer(300, true)
 		, serial(Anope::CurTime)
-		, cur_id(rand())
+		, cur_id(Anope::RandomNumber())
 	{
 	}