mlsys_parse_text_ uses an old convention for handling 2-digit years

[Eric Swenson]

mlsys_parse_text_, when parsing the email envelopes (headers), uses an old convention when encountering 2-digit years to convert to 4-digit years. It simply adds 1900 to the 2-digit year. These days, the better convention is to check for years less than 50, and for those, to add 2000, otherwise 1900.

[Eric Swenson]

​https://s3.amazonaws.com/eswenson-multics/public/mcrs/MCR10168.pdf