hgweb: urlescape all urls, HTML escape repo/tag/branch/... names
Without this, repository paths or names containing e.g. & characters or html
tags yielded strange results, possibly allowing cross-site scripting attacks.
<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>