NAME: 
  clscan
 PURPOSE:
  Scan a group of raw OSIRIS XD frames and find rough spectral location.
 DESCRIPTION:
 CATEGORY:
  Spectroscopy
 CALLING SEQUENCE:
  clscan,calib,root,start,last,frno,mate,RANGE=range,PATH=path
 INPUTS:
  calib- Anonymous structure containing all pertinent calibration
           information.  This structure is usually loaded beforehand using
           the routine, "ldcalir"
  root - string containing the root of the file name (with leading path
         if desired).  DO NOT include the . between the root and suffix.
  start  - First spectrum number of sequence to scan.
  last   - Last spectrum number of sequence to scan, if negative, this number
             is taken to be the number of spectra to scan.
 OPTIONAL INPUT PARAMETERS:
 KEYWORD INPUT PARAMETERS:
  PATH - optional string that points to the directory containing the data.
           This information is not used if the root already begins with '/'.
           If root is not an absolute pathname, then PATH is prepended to
           root for READ operations.  This path is not used for saving.
           This allows reading from one directory (possible a read only area)
           and then saving to the current directory.
  XRANGE - range of column numbers to average in extracted spectral slice to
           find rough location of spectrum.  Default is all columns.
  YRANGE - range of rows that are valid locations.  Default is all rows but the
           first and last.
  EXCLUDE- List of frames in the indicated range that should be excluded from
           consideration.

 OUTPUTS:
  frno - A vector of frame numbers.
  mate - A vector that gives a suggested frame number from this set for
           a sky pair match that does not overlap the object.
  
  Also, information on location for each spectrum is printed to the console.

 KEYWORD OUTPUT PARAMETERS:
 COMMON BLOCKS:
 SIDE EFFECTS:
 RESTRICTIONS:
  Specifically written for OSIRIS cross-dispersed spectral data.
 PROCEDURE:
 MODIFICATION HISTORY:
  95/09/27, Written by Marc W. Buie, Lowell Observatory
  96/05/29, MWB, changed 4th argument from NSPEC to LAST.
  97/08/07, MWB, removed RANGE (buggy) and added XRANGE and YRANGE
  97/12/10, MWB, fixed a really nasty bug that corrupt the location for
                   very high signal-to-noise data.
  98/07/01, MWB, added code to skip over missing files in sequence.