Update vendor directory

Re-added cobra patch 499475bb41

vendor/golang.org/x/crypto/ssh/terminal/terminal.go

@@ -772,8 +772,6 @@ func (t *Terminal) readLine() (line string, err error) {
 
 		t.remainder = t.inBuf[:n+len(t.remainder)]
 	}
-
-	panic("unreachable") // for Go 1.0.
 }
 
 // SetPrompt sets the prompt to be used when reading subsequent lines.
@@ -922,3 +920,32 @@ func (s *stRingBuffer) NthPreviousEntry(n int) (value string, ok bool) {
 	}
 	return s.entries[index], true
 }
+
+// readPasswordLine reads from reader until it finds \n or io.EOF.
+// The slice returned does not include the \n.
+// readPasswordLine also ignores any \r it finds.
+func readPasswordLine(reader io.Reader) ([]byte, error) {
+	var buf [1]byte
+	var ret []byte
+
+	for {
+		n, err := reader.Read(buf[:])
+		if n > 0 {
+			switch buf[0] {
+			case '\n':
+				return ret, nil
+			case '\r':
+				// remove \r from passwords on Windows
+			default:
+				ret = append(ret, buf[0])
+			}
+			continue
+		}
+		if err != nil {
+			if err == io.EOF && len(ret) > 0 {
+				return ret, nil
+			}
+			return ret, err
+		}
+	}
+}