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.
<table class="changelogEntry parity#parity#">
<tr>
<th class="age">#date|age# ago:</th>
<th class="firstline">#desc|firstline|escape#</th>
</tr>
<tr>
<th class="changesetRev">changeset #rev#:</th>
<td class="changesetNode"><a href="?cmd=changeset;node=#node#">#node|short#</a></td>
</tr>
#parent#
#changelogtag#
<tr>
<th class="author">author:</th>
<td class="author">#author|obfuscate#</td>
</tr>
<tr>
<th class="date">date:</th>
<td class="date">#date|date#</td>
</tr>
<tr>
<th class="files"><a href="?cmd=manifest;manifest=#manifest#;path=/">files</a>:</th>
<td class="files">#files#</td>
</tr>
</table>