NAME:
	getradec_wfs
 PURPOSE:
       turns xi and xn (position relative to a reference pixel crval in 
	tangent frame) into ra (hrs) and dec(deg)
 CALLING SEQUENCE:
	getradec_wfs,xi,xn,ra,dec,crval
 INPUTS:
	xi:	x coordinate in arcsecs relative to reference pixel
	xn:	y corrdinate in arcsecs relative to reference pixel
	crval:	2 elements fltarr, position of reference pixel in degrees
 OUTPUTS:
	ra:	right ascension (decimal hours)
	dec:	declination (decimal degrees)
 EXAMPLE:
	getradec_wfs,xi,xn,ra,dec,ast.crval
 RESTRICTIONS:
	UNTESTED
 CALLED PROCEDURES:
	astrolib routines
 MODIFICATION HISTORY:
	Oct-2000  Original by Suzanne Aigrain, copied from fit2txt.pl*

(See /home/xmmssc/soft/idl/pro/astro/getradec_wfs.pro)