gtk/docs/tools

The doc shooter is used to take screenshots of widgets for the GTK
reference manuals.  We use these images for both the headers of the
images, and for the visual index of GNOME images.  They aren't part of
the docs build.  Instead, the images are taken, and then copied by hand
into gtk/docs/reference/gtk/images/

Ideally, the images should be taken once a release, and all images
should be updated at the same time.  A simple theme should be used to
take the screenshots, and in the future, we may include a gtkrc file in
this directory for the shooter to use.  Currently, all shots are
constrained to the same width.  Care should be taken when adding new
widgets to keep this constraint.