net: make listen/bind errors more informative

vlib/net/errors.v

@@ -20,6 +20,10 @@ pub const (
 	err_timed_out_code      = errors_base + 9
 )
 
+pub fn socket_error_message(potential_code int, s string) ?int {
+	return socket_error(potential_code) or { return error('$err.msg; $s') }
+}
+
 pub fn socket_error(potential_code int) ?int {
 	$if windows {
 		if potential_code < 0 {