subroutine:     GDSD_GRlog

purpose:        read a descriptor from a specified level

category :	header

file:   gdsd_grxxx.c

author: Do Kester	do@guspace.rug.nl

use:    call gdsd_grlog( 
             set_id,    I     	character*(*)
             key,       I     	character*(*)
	     axes,	I     	integer(n)
	     grid,	I	integer(n)
	     n,		I	integer
	     value,	O	logical
	     error )	O	integer

        set_id 		name to search the key in
        key		gds_descriptor to search for
	axes		list of defined axes 
			axes which are not mentioned are undefined
	grid		list of grid positions on the specified axes
	n		number of defined axes and grids
	value		returned value; 
			if not found value remains as it was upon input
        error 		if succesful: level where the item was found
			if not: error code as in GDSD_Rxxx

description:    

externals:      GDSD_Rxxx 

updates:        15/11/90 DK, code