RE: entity mib support for tcif

If this proposal is adopted, it looks like we need a DateAndTimeOrNul TC, for these systems that do not support manufacture date for some reason. 

Dan

> 
> entPhysicalMfgDate   OBJECT-TYPE
>       SYNTAX      DateAndTime
>       MAX-ACCESS  read-only
>       STATUS      current
>       DESCRIPTION
>               "The manufacturing date for the physical entity."
>       ::= { entPhysicalEntry xx }