fix an exception in gpg.py with multiples sigs for the same cset
- silly error, do not overwrite the variable we use for iterating
- correct 'hg help sign'
<item>
<title>#desc|strip|firstline|strip|escape#</title>
<link>#url#?f=#filenode|short#;file=#file|urlescape#</link>
<description><![CDATA[#desc|strip|escape|addbreaks#]]></description>
<author>#author|obfuscate#</author>
<pubDate>#date|rfc822date#</pubDate>>
</item>