templates/map-rss

Update [extdiff] configuration sample for vimdiff,
taking acount cmd.xxx and opts.xxx configurations item.

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