Adds support for error element on message and presence

message.go

@@ -14,6 +14,7 @@ type Message struct {
 	Subject string `xml:"subject,omitempty"`
 	Body    string `xml:"body,omitempty"`
 	Thread  string `xml:"thread,omitempty"`
+	Error   Err    `xml:"error,omitempty"`
 }
 
 func (Message) Name() string {

presence.go

@@ -11,7 +11,7 @@ type Presence struct {
 	Show     string `xml:"show,attr,omitempty"` // away, chat, dnd, xa
 	Status   string `xml:"status,attr,omitempty"`
 	Priority string `xml:"priority,attr,omitempty"`
-	//Error    *clientError
+	Error    Err    `xml:"error,omitempty"`
 }
 
 func (Presence) Name() string {