SXADDHIST
Name
	SXADDHIST                           
Purpose
	Procedure to add HISTORY (or COMMENT) line(s) to a FITS header
Explanation
     
       The advantage of using SXADDHIST instead of SXADDPAR is that with 
      
       SXADDHIST many HISTORY or COMMENT records can be added in a single call.
Calling Sequence
	sxaddhist, history, header, [ /PDU, /COMMENT ]
Inputs
	history - string or string array containing history or comment line(s)
		to add to the FITS header
Input/output
	header - FITS header (string array).   Upon output, it will contain the
              
               specified HISTORY records added to the end
Optional Keyword Inputs
     
       /BLANK - If specified then blank ('       ') keywords will be written
              
              rather than 'HISTORY ' keywords.
      
       /COMMENT - If specified, then 'COMMENT ' keyword will be written rather
              
              than 'HISTORY ' keywords.    
              
              Note that according to the FITS definition, any number of 
              
              'COMMENT' and 'HISTORY' or blank keywords may appear in a header,
              
              whereas all other keywords may appear only once.   
	LOCATION=key - If present, the history will be added before this
	       keyword.  Otherwise put it at the end.
	/PDU - if specified, the history will be added to the primary
		data unit header, (before the line beginning BEGIN EXTENSION...)               
		Otherwise, it will be added to the end of the header.
              
               This has meaning only for extension headers using the STScI
              
               inheritance convention. 
Outputs
	header - updated FITS header
Examples
	sxaddhist, 'I DID THIS', header      ;Add one history record
	hist = strarr(3)
	hist[0] = 'history line number 1'
	hist[1[ = 'the next history line'
	hist[2] = 'the last history line'
	sxaddhist, hist, header              ;Add three history records
Side Effects
     
       Header array is truncated to the final END statement
	LOCATION overrides PDU.
History
	D. Lindler  Feb. 87
	April 90  Converted to new idl  D. Lindler
	Put only a single space after HISTORY   W. Landsman  November 1992
	Aug. 95	  Added PDU keyword parameters
	Converted to IDL V5.0   W. Landsman   September 1997
	LOCATION added.  M. Greason, 28 September 2004.