Generate avatar-facing API shims

crates/libremetaverse-types/src/compat.rs

@@ -130,3 +130,7 @@ pub struct StringWriter(pub String);
 
 #[derive(Clone, Copy, Debug, Eq, Hash, PartialEq)]
 pub struct TypeId(pub &'static str);
+
+pub struct Span<T>(pub PhantomData<fn(T)>);
+
+pub struct RandomSource;