icon-slicer is a utility for generating icon themes and libXcursor cursor
themes.

The inputs to icon-slicer are conceptually:
 A) a set of multi-layer images, one for each size
 B) a XML theme description file

Each image contains all the cursors arranged in a grid; for cursors the
layers are:
 - a layer with a dot for the hotspot of each cursor
 - the main image or first animation frame for multi-frame animated cursors
 - the second animation frame for multi-frame animated cursors

For icons, the layers are:
 - a layer with the images
 - an optional layer with attachment points for emblems
 - an optional layer with boxes for embedding text into icons

In practice, since loading of multilayer images is not supported by standard
image libraries, each layer is input as a separate image file.