SuperC features for the year 2000 transition

SuperC includes features designed to help manage the Year 2000 transition:

Specify a 100-year period (or "year window") so that, for dates that have only a 2-digit year, the century can be determined. This can be based on either:
- A "fixed" year window (with a fixed starting year), or
- A "sliding" year window (starting at a specified number of years before the current year).
Compare 2-digit year values in one data set with 4-digit year values in another data set.
Compare compressed year values in one data set with uncompressed year values in another data set.
Filter cosmetic differences caused by adding century digits to 2-digit years, so that you can more easily identify real differences in content.