NAME:
  mkcircle
 PURPOSE:   (one line only)
  Compute points that lie on a circle
 DESCRIPTION:
 CATEGORY:
  Miscellaneous
 CALLING SEQUENCE:
  mkcircle,xcenter,ycenter,radius,x,y
 INPUTS:
  xcenter - Scalar, x position of the center of the circle
  ycenter - Scalar, y position of the center of the circle
  radius  - Radius of the circle
 OPTIONAL INPUT PARAMETERS:
  NPTS    - Number of points along the circle (default=100)
             Note that the first point and the last point are identical
             and that the length of the output vector is 1 larger than
             the value for NPTS.
 KEYWORD INPUT PARAMETERS:
 OUTPUTS:
  x - vector with the points
  y - vector with the points
 KEYWORD OUTPUT PARAMETERS:
 COMMON BLOCKS:
 SIDE EFFECTS:
 RESTRICTIONS:
 PROCEDURE:
 MODIFICATION HISTORY:
  Written by Marc W. Buie, Southwest Research Institute, 2013/03/06