Bug 584983 mark deprecated exthandler interfaces and methods with [deprecated]

r=biesi

uriloader/exthandler/nsIExternalProtocolService.idl

@@ -127,9 +127,10 @@ interface nsIExternalProtocolService : nsISupports
    * Used to load a url via an external protocol handler (if one exists)
    *
    * @param aURL The url to load
+   *
    * @deprecated Use LoadURI instead (See Bug 389565 for removal)
    */
-   void loadUrl (in nsIURI aURL);
+   [deprecated] void loadUrl(in nsIURI aURL);
 
   /**
    * Used to load a URI via an external application. Might prompt the user for