-Combine entries in the property sheets and make it a bit more flexible,
and drop some redundant items
-Use Custom Build Rules for generating enumeration and marshalling sources,
and the .def file so that they can be wiped off when a "clean" is
requested, and regenerate automatically when the templates/.symbols
files are updated.
-Improve consistency by using ApiVersion rather than ClutterApiVersion
with the Visual Studio project for other components of the Clutter/GTK+
stack
-Get rid of unneeded configs in the "install" project
-Add configuration in Clutter projects to add option to build Clutter with
the GDK3 backend in addition to the Win32 backend
-Add another preconfigured clutter-config.h.win32_GDK which contains
backend configs for both GDK3 and Win32 windowing and input.
