Change log Tool_image for AIPS++ version 1.9

A summary of the changes is available.

Change-id:  0158
Author:     Neil Killeen
Date:       2003/11/24
Area:       Tool    image
Category:   New Code
Summary:    New LEL function INDEXIN

A new LEL function, INDEXIN has been written that can be used with the 'mask' argument of the Image tool. It allows you to select based on pixel indices (rather than pixel values) Neil & Ger

Change-id:  0159
Author:     Neil Killeen
Date:       2003/12/15
Area:       Tool    image
Category:   New Code,Documentation
Summary:    Added new Image tool function 'structurefunction'

I have added a new Image tool function called 'structurefunction' to compute the structure function of an image