mq: fix queue.apply to not call os.chdir()
call to os.chdir broke "hg -R dirname qpush".
instead pass -d (change directory) option to patch command.
<item>
<title>#tag|escape#</title>
<link>#url#?cs=#node|short#</link>
<description><![CDATA[#tag|strip|escape|addbreaks#]]></description>
<pubDate>#date|rfc822date#</pubDate>
</item>