Some work on the testsuite

The testsuite runs with SBCL and CCL on Linux without problems.
Correcting two typos
Some work on the demo for an application window.
Rework the implemenation of ensure-gtk-main.

This implementation works on Linux and Windows, but it is not clear what
the best implementation would be.
Correcting a typo
Some work on the documentation
Adding a file for GtkNumerableIcon
Adding files for GEmbledIcon and GEmblem
Do not initialize gdk-threads when loading the library