NAME:
  listcor
 PURPOSE:   (one line only)
  Correlate two string lists
 DESCRIPTION:
 CATEGORY:
  Miscellaneous
 CALLING SEQUENCE:
  listcor,list1,list2,ind1,ind2,nind1
 INPUTS:
  list1 - 1-D array of strings.  The program will run faster if this
             is the shorter of the two lists.
  list2 - 1-D array of strings
 OPTIONAL INPUT PARAMETERS:
 KEYWORD INPUT PARAMETERS:
  UNIQUE - flag, if set forces the output mapping to be one-to-one.
           If there are multiple matches, the first is kept as defined by
           the order in which the entries are in the lists.  If this is
           not set, all matches in list2 are reported to the item in list1.
 OUTPUTS:
  ind1 - Index of matches in the first list
  ind2 - Index of matches in the second list
  nind1 - Index into the first list that doesn't match anything in the second
             If you want to get the opposite result, run this again with the
                lists reversed.
 KEYWORD OUTPUT PARAMETERS:
 COMMON BLOCKS:
 SIDE EFFECTS:
 RESTRICTIONS:
 PROCEDURE:
 MODIFICATION HISTORY:
  2016/09/12, Written by Marc W. Buie, Southwest Research Institute