NAME:
  fitsbin
 PURPOSE:
  Software binning of an image in FITS file format.
 DESCRIPTION:

 CATEGORY:
  CCD data processing
 CALLING SEQUENCE:
  fitsbin,file,INPATH=inpath,OUTPATH=outpath,BINFAC=binfac
 INPUTS:
  file - String (or array) of name of file to be binned.  If the file name
            includes a trailing .fits, the .fits is option on the file name.
            The output file name will not include the .fits tag.
 OPTIONAL INPUT PARAMETERS:
  BINFAC  - Binning factor (default=2).

  INPATH  - String, path to directory where data are to be read from.
               Default=current directory

  OUTPATH - String, path to directory where data are to be written.
               Default=current directory

  Note: if INPATH and OUTPATH end up being the same, then outpath is
            changed by adding the directory name, binned, the end of the
            path.  WARNING: No attempt is made to resolved different means
            of expressing the same directory.  The test is made just by
            a simple string comparison.
 KEYWORD INPUT PARAMETERS:

 OUTPUTS:

 KEYWORD OUTPUT PARAMETERS:

 COMMON BLOCKS:

 SIDE EFFECTS:

 RESTRICTIONS:

 PROCEDURE:

 MODIFICATION HISTORY:
  Written by Marc W. Buie, Lowell Observatory, 2000/06/22
  2003/10/01, MWB, converted to IDL file_mkdir calls