/* $DOC$
   $NAME$
      ft_IsShare()
   $CATEGORY$
      DOS/BIOS
   $ONELINER$
      Determine if DOS "Share" is installed
   $SYNTAX$
      ft_IsShare() -> nRetCode
   $ARGUMENTS$
      None
   $RETURNS$
      nRetcode will be set as follows on exit:

          0 if SHARE not loaded but ok to load
          1 if SHARE not loaded and not ok to load
        255 if SHARE loaded
   $DESCRIPTION$
      Uses DOS interrupt 2Fh (MultiPlex interrupt), service 10h
      to determine if DOS SHARE.COM is loaded.
   $EXAMPLES$
      IF ft_IsShare() != 255
         ? "SHARE must be loaded!"
      ENDIF
   $SEEALSO$
      ft_int86()
   $END$
 */