log/syslog: fix typo: change Wanring to Warning

R=golang-dev, r
CC=golang-dev
https://golang.org/cl/11220044

src/pkg/log/syslog/syslog.go

@@ -203,7 +203,7 @@ func (w *Writer) Err(m string) (err error) {
 	return err
 }
 
-// Wanring logs a message with severity LOG_WARNING, ignoring the
+// Warning logs a message with severity LOG_WARNING, ignoring the
 // severity passed to New.
 func (w *Writer) Warning(m string) (err error) {
 	_, err = w.writeAndRetry(LOG_WARNING, m)