Export the logger (again)

Just enabling or disabling logging falls short of the power of
interfaces of go. A user is forced to either accept the logging to
stderr in the format defined by xgb or disable logging alltogether. By
exporting the logger, we can actually let the user decide where to log
in what format.

nexgb/conn.go

@@ -33,8 +33,8 @@ func (c *Conn) connect(display string) error {
 	authName, authData, err := readAuthority(c.host, c.display)
 	noauth := false
 	if err != nil {
-		logger.Printf("Could not get authority info: %v", err)
-		logger.Println("Trying connection without authority info...")
+		Logger.Printf("Could not get authority info: %v", err)
+		Logger.Println("Trying connection without authority info...")
 		authName = ""
 		authData = []byte{}
 		noauth = true