ui: inline _writenobuf() into write() due to performance issue
I'll remove redundant conditions later in this series.
<item>
<title>{branch|escape}</title>
<link>{urlbase}{url|urlescape}rev/{node|short}</link>
<description><![CDATA[{branch|strip|escape|addbreaks}]]></description>
<pubDate>{date|rfc822date}</pubDate>
</item>