Add new error and fmt it

msg.go

@@ -27,7 +27,8 @@ import (
 const maxCompressionOffset = 2 << 13 // We have 14 bits for the compression pointer
 
 var (
-	ErrFqdn        error = &Error{Err: "domain must be fully qualified"}
+	ErrFqdn      error = &Error{Err: "domain name must be fully qualified"}
+	ErrDomain    error = &Error{Err: "domain name must be 255 or less bytes long"}
 	ErrId        error = &Error{Err: "id mismatch"}
 	ErrRdata     error = &Error{Err: "bad rdata"}
 	ErrBuf       error = &Error{Err: "buffer size too small"}