Clean up date and timezone handling. We used to pass changelog dates around as a "unixtime timezone" string containing a pair of encoded ints. Now, they get passed around as a (unixtime, timezone) tuple of numbers, which makes much more sense.

default = "changelog"
header = header-rss.tmpl
changelog = changelog-rss.tmpl
changelogentry = changelogentry-rss.tmpl
filelog = filelog-rss.tmpl
filelogentry = filelogentry-rss.tmpl