templates/map-rss

[extendedchangelog] add extra metadata in the changelog entry

- add a third item in the date field that holds arbitrary
  key:value items

default = 'changelog'
header = header-rss.tmpl
changelog = changelog-rss.tmpl
changelogentry = changelogentry-rss.tmpl
filelog = filelog-rss.tmpl
filelogentry = filelogentry-rss.tmpl
tags = tags-rss.tmpl
tagentry = tagentry-rss.tmpl