Fix problems with newlines in feed title

The feeds of http://www.zeit.de/hilfe/hilfe#rss (major newspaper) all have titles starting with a newline. This isn't pretty but within the specification. Tiny has problems unsubscribing from such feeds.

Feeds with more whitespace, maybe around URLs, would probably cause more problems. It should be safe to `$this->doc->preserveWhiteSpace = false`, but I can't test that.