Increase max curls to number of mining threads + queue * 2, accounting for up and downstream comms.

cgminer.c

@@ -2219,7 +2219,7 @@ static void recruit_curl(struct pool *pool)
  * network delays/outages. */
 static struct curl_ent *pop_curl_entry(struct pool *pool)
 {
-	int curl_limit = opt_delaynet ? 5 : mining_threads * 4 / 3;
+	int curl_limit = opt_delaynet ? 5 : (mining_threads + opt_queue) * 2;
 	struct curl_ent *ce;
 
 	mutex_lock(&pool->pool_lock);