fix appendfile problem on macos.
when i open file with mode 'a+' on linux, seek position is 0.
on macos seek position is end of file instead. not documented.
<table class="parity#parity#" width="100%" cellspacing="0" cellpadding="0">
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<td align="right" width="15%"><b>#date|age# ago: </b></td>
<td><b><a href="?cs=#node|short#">#desc|strip|firstline|escape#</a></b></td></tr>
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<td align="right">revision #filerev#: </td>
<td><a href="?f=#filenode|short#;file=#file|urlescape#">#filenode|short#</a>
<a href="?fd=#node|short#;file=#file|urlescape#">(diff)</a>
<a href="?fa=#filenode|short#;file=#file|urlescape#">(annotate)</a>
</td></tr>
#rename%filelogrename#
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<td align="right">author: </td>
<td>#author|obfuscate#</td></tr>
<tr>
<td align="right">date: </td>
<td>#date|date# (#date|age# ago)</td></tr>
</table>