Change shift expressions to unsigned types. Shifting signed values to

a result that is not representable has undefined behaviour.

code/server/sv_client.c

@@ -140,7 +140,7 @@ void SV_GetChallenge(netadr_t from)
 	}
 
 	// always generate a new challenge number, so the client cannot circumvent sv_maxping
-	challenge->challenge = ( (rand() << 16) ^ rand() ) ^ svs.time;
+	challenge->challenge = ( ((unsigned int)rand() << 16) ^ (unsigned int)rand() ) ^ svs.time;
 	challenge->wasrefused = qfalse;
 	challenge->time = svs.time;