Allow specifying non-derivable classes in glib_wrapper!()
Allow specifying non-derivable classes in glib_wrapper!()

As before, we can have

    pub struct Foo(Object<ffi::Foo>);

in the macro call; this now means that there is no class struct
available.  To specify class structs,

    pub struct Foo(Object<ffi::Foo, ffi::FooClass>);

rust-gnome/glib,EPashkin/rust-gnome-glib