Convert a YYYYMMDD string to a Clipper date.
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 Syntax

        GT_SToD(<cDateString>) --> dClipperDate

 Arguments:

      <cDateString> is a string in the same format as that returned by
      the Clipper function dtos(). The format is "YYYYMMDD" where "YYYY"
      is the year, "MM" is the month and "DD" is the day.

 Returns:

      A Clipper date.

 Description:

      GT_SToD() can be used to convert a string date into a Clipper date
      variable. This is of use if you wish to hard code a date into a
      program but you don't know what date format will be used.

 Examples:

      set date    british
      set century off
      dDate := GT_SToD("19671209")
      ? dDate                         // Prints `09/12/67'

 Source: STOD.C

 Author:  Dave Pearson