NAME:
  wroblist
 PURPOSE:
  Write an object list to a file.
 DESCRIPTION:

 CATEGORY:
  Astrometry
 CALLING SEQUENCE:
  wroblist,file,nobj,filelist,dt,offset,pos,flags,idstr,nf
 INPUTS:
  file - String of file name to be written to.
  nobj     - number of objects in list.
  filelist - string array of file names for this object list.
  dt       - nfiles-1 element vector with the time, in hours of each file
               relative to the time of the first frame.  Since the first frame
               is identically 0, this value isn't saved.
  offset   - 2*(nfiles-1) element vector [x,y offset (B-A),
                x,y offset (C-A), ...]
  pos      - [2*nfiles,nobj] element vector, each row is set of
                positions [x1,y1,x2,y2,x3,y3]
  flags    - nobj element vector of flags either ?, y, or n.
  idstr    - String that identifies the measurement in some way.
  nf       - number of files in set.
 OPTIONAL INPUT PARAMETERS:

 KEYWORD INPUT PARAMETERS:

 OUTPUTS:

 KEYWORD OUTPUT PARAMETERS:

 COMMON BLOCKS:

 SIDE EFFECTS:

 RESTRICTIONS:

 PROCEDURE:

 MODIFICATION HISTORY:
  1998/11/3, Written by Marc W. Buie, Lowell Observatory
  1999/1/29, MWB, added idstr
  1999/2/29, MWB, added dt and version tag in file