Set the attributes of a file.
──────────────────────────────────────────────────────────────────────────────

 Syntax

        GT_FAttrib(<cFileName>,<cAttributes>) --> lChangedOk

 Arguments:

      <cFileName> is the name of the file who's attributes are to be
      changed.

      <cAttributes> are the attributes to be set.

 Returns:

      A logical value, .T. if the file attributes were changed ok, .F.
      if not.

 Description:

      GT_FAttrib() can be used to set the attributes of a file.

      The available attributes that can be changed are:

                     ─────────────────────────
                     Character       Attribute
                     ─────────────────────────
                     A               Archive
                     H               Hidden
                     S               System
                     R               Read Only
                     ─────────────────────────

      To set an attribute on use the upper case letter, to set the
      attribute off use the lower case letter. Any attribute that
      is not included in the attribute string is left as it is.

 Examples:

      // Make a file read only.

      lOk := GT_FAttrib("Life.42","R")

      // Turn on the archive attribute and the hidden attrubite, and
      // turn off the read only attribute.

      lOk := GT_FAttrib("Life.42","AHr")

 Source: SETFATTR.C

 Author:  Dave Pearson