Additional namespaces are omitted from rss tag

When reading a feed with additional NSs in the RSS tag definition, these are omitted from the feed.

For example, the RSS tag <rss xmlns:itunes="http://www.itunes.com/dtds/podcast-1.0.dtd" xmlns:googleplay="http://www.google.com/schemas/play-podcasts/1.0" version="2.0> results in <rss version="2.0"> being generated so that the original additional namespaces have to be added manually via addNS() afterwards.