Function:     IRDS_MERGE

Purpose:      merge IRDSX in IRDS

Category:     IRAS

File:         irds_merge.c

Author:       Do Kester

Use:          call irds_merge( 
                        irdsx,    I     character*(*)
                        irds,     I/O   character*(*)
                        status )  I/O   integer
        irdsx   name of irds to merge with IRDS
        irds    name of irds to merge in
        status   0 : OK. 
		-1 : both nonexistent
                -2 : the two IRDS's dont pertain to the same plate
		-3 : not the same instrument
		-4 : partly or non existing IRDS

description:    
	IRDSX and IRDS should pertain to the same plate i.e. all the
	output parameters obtained with irds_enquire should be the
	same. If not the subroutine returns with status = -2.
	The snips in the two IRDS's which have the same sop/att
	combination are glued into one; blank values are filled 
	in between if the two are not adjacent in time. 
	The final IRDS will have a minimal snip duration, necessary 
	to fit all the snips in IRDS.
	The snips remain in increasing order of sop and att.

externals:      

updates:        23/02/90 DK, document creation
		13/11/90 DK, code
		06/02/91 DK, make global variables and functions `static'
		08/03/91 DK, copy NOISE descriptors too
		12/02/92 FL, also copy BPHF data
		26/02/92 DK, copy SCANTYPE
		03/03/92 DRB,copy OBS
		18/03/92 FL, new enquire_snip and extend, so copying OBS,
		             SCANTYPE and PLATE obsolete.
		07/05/92 DK, flag error for cripple IRDS's
		11/03/93 DK, delete partial irds and use userfio