NAME:
  editmask
 PURPOSE:   (one line only)
  Interactive image-based editing of a bad-pixel mask
 DESCRIPTION:
 CATEGORY:
  CCD data processing
 CALLING SEQUENCE:
  editmask,image,mask
 INPUTS:
  image - Array containing image, this argument is not modified.
  mask  - Array containing initial mask.  This does not need to exist
            prior to calling this routine.  This argument is modified.
 OPTIONAL INPUT PARAMETERS:
 KEYWORD INPUT PARAMETERS:
  XSIZE - size of the main image window
  YSIZE - size of the main image window
  BITMASK - This is a mask that contains the bit (or bits) to be set
              (or cleared) in the mask.  Normally, this mask will have
              a single bit set.  The input must be a byte type scalar.
              Default='01'xb (bit 0 set).
  STYLE - This indicates how the bitmask information is to be visually
            applied to the image.
              0 - blot out pixel with red (default)
              1 - replace pixel with sky value
          This used only for visual purposes.  The image is not actually
            modified here.
 OUTPUTS:
  mask  - Edited version of the mask
 KEYWORD OUTPUT PARAMETERS:
 COMMON BLOCKS:
 SIDE EFFECTS:
 RESTRICTIONS:
 PROCEDURE:
 MODIFICATION HISTORY:
  Written by Marc W. Buie, Southwest Research Institute, 2011/09/21