print the index key variable or expression for that column.  It was mistakenly
printing ASC/DESC/NULLS FIRST/NULLS LAST decoration too --- and not only for
the target column, but all columns.  Someday we should have an option to
extract that info (and the opclass decoration as well) for a single index
column ... but today is not that day.  Per bug #3829 and subsequent
discussion.