jingle_message, muc, presence, version: Always use the check_no_attributes macro.

src/muc/muc.rs

@@ -25,6 +25,7 @@ impl TryFrom<Element> for Muc {
         if !elem.is("x", ns::MUC) {
             return Err(Error::ParseError("This is not an x element."));
         }
+        check_no_attributes!(elem, "x");
 
         let mut password = None;
         for child in elem.children() {
@@ -35,10 +36,6 @@ impl TryFrom<Element> for Muc {
             }
         }
 
-        for _ in elem.attrs() {
-            return Err(Error::ParseError("Unknown attribute in x element."));
-        }
-
         Ok(Muc {
             password: password,
         })