FRU board mfg. date uses a different value for 'unspecified'
timestamp than the general IPMI specification.
This commit makes ekanalyzer and fru commands process unspecified
FRU dates properly, displaying 'Unspecified' instead of
'Mon Jan 1 03:00:00 1996'.
Resolvesipmitool/ipmitool#57
Signed-off-by: Alexander Amelkin <alexander@amelkin.msk.ru>