When using custom fields for smart group criteria, relative dates create static dates instead

We check to see if the field matches the pattern _date_relative and if so, we record that it's a relative date field when we save the search.

However, custom fields come through in the form: custom_13_relative so they don't match and thus are not treated as relative dates.

Since the UI on the search form gives the impression that they are relative dates (same drop down as the relative dates for activity, contribution, etc) it leads to user confusion.