Add Debug flag to Config

I'll use this to squash the noisy logging for people who don't care.

client.go

@@ -1756,7 +1756,7 @@ func (me *Client) addConnection(t *torrent, c *connection) bool {
 		if c == nil {
 			return false
 		}
-		if missinggo.CryHeard() {
+		if me.config.Debug && missinggo.CryHeard() {
 			log.Printf("%s: dropping connection to make room for new one:\n    %s", t, c)
 		}
 		c.Close()

config.go

@@ -47,4 +47,6 @@ type Config struct {
 
 	IPBlocklist *iplist.IPList
 	DisableIPv6 bool
+	// Perform logging and any other behaviour that will help debug.
+	Debug bool
 }