Interfaces are going to reference each other across namespaces, so this
implements a type lookup with the full name.

It supports the following idl syntax in WinRT mode:

    #ifdef __WIDL__
    #pragma winrt ns_prefix
    #endif

    import "wtypes.idl";

    namespace Windows {
        namespace Foo {
            [object]
            interface IFoo {}
        }
        namespace Bar {
            [object]
            interface IBar { HRESULT DoBar([in] Windows.Foo.IFoo *foo); }
        }
    }

That was previously failing to parse the Windows.Foo.IFoo part and to
lookup the corresponding type.
Signed-off-by: Rémi Bernon <rbernon@codeweavers.com>
Signed-off-by: Alexandre Julliard <julliard@winehq.org>