[PATCH v8] Allow commit date before Unix epoch, clean fix for (issue2513)

[Yuya Nishihara]

On Fri, 8 Apr 2016 18:05:13 +0200, Florent Gallaire wrote:
> # HG changeset patch
> # User Florent Gallaire <fgallaire at gmail.com>
> # Date 1460131286 -7200
> #      Fri Apr 08 18:01:26 2016 +0200
> # Node ID 9060da16455219aec0bd8ed277c4eee5555266bc
> # Parent  c5565fc8848dd084d104ca40c33d1acdfcff8bc6
> date: reallow negative timestamp, fix for Windows buggy gmtime() (issue2513)

This patch is getting bigger, and we prefer small patches that do one
functional change per patch.

https://www.mercurial-scm.org/wiki/ContributingChanges#Organizing_patches

Can you make a separate patch to fix boundary check of negative integer?