// ReadCodeLine reads a response code line of the form
// code message
-// where code is a 3-digit status code and the message
+// where code is a three-digit status code and the message
// extends to the rest of the line. An example of such a line is:
// 220 plan9.bell-labs.com ESMTP
//
// ...
// code message line n
//
-// where code is a 3-digit status code. The first line starts with the
+// where code is a three-digit status code. The first line starts with the
// code and a hyphen. The response is terminated by a line that starts
// with the same code followed by a space. Each line in message is
// separated by a newline (\n).