archival: add "extended-timestamp" extra block for zip archives (issue3600) Before this patch, zip archives created by "hg archive" are extracted with unexpected timestamp, if TZ is not configured as GMT. This patch adds "extended-timestamp" extra block to zip archives, and unzip will extract such archives with timestamp specified in added extra block, even though TZ is not configured as GMT. Please see documents below for detail about specification of zip file format and "extended-timestamp" extra block: http://www.pkware.com/documents/casestudies/APPNOTE.TXT http://www.opensource.apple.com/source/zip/zip-6/unzip/unzip/proginfo/extra.fld Original implementation of this patch was suggested by "Jun Omae <jun66j5@gmail.com>".