Julia bindings using libgobject-introspection.

This is still in a very early stage.

What works:

• GObject types, with constructors and methods (including property accessors)
• passing of numeric types, string constants, gobjects
• runtime type-determination of returned GObject pointers
• Full type compatibility with Gtk.jl
• properties and signal handling (from Gtk.jl)
• constants and enums/flags
• multiple return values using c-pointers
• Basic error handling

What needs to be done:

• passing of arrays
• memory management still quite rough
• proper support for structs and abstract interfaces
• consistent naming of things
• callback parameters
• much more...