archive: set date to 1980 for very old zip files
The zip file format stores the date using "MS-DOS format" which
apparently means that they use 1980 as their epoch. Python's zipfile
module emits deprecation warnings of this form
/usr/lib/python2.6/zipfile.py:1108: DeprecationWarning: struct
integer overflow masking is deprecated
self.fp.write(zinfo.FileHeader())
/usr/lib/python2.6/zipfile.py:1108: DeprecationWarning: 'H' format
requires 0 <= number <= 65535
self.fp.write(zinfo.FileHeader())
/home/mg/src/mercurial-crew/mercurial/archival.py:169:
DeprecationWarning: struct integer overflow masking is deprecated
self.z.close()
/home/mg/src/mercurial-crew/mercurial/archival.py:169:
DeprecationWarning: 'H' format requires 0 <= number <= 65535
self.z.close()
when it is given such old timestamps. This fixes this by silently
clamping the date to 1980.