Add some base VM implementations

Some instructions are currently implemented. Others are not. This is
mostly just a checkpoint so I can implement lexical name definitions.

Signed-off-by: Alek Ratzloff <alekratz@gmail.com>

src/obj/fun.rs

@@ -32,6 +32,9 @@ pub static CALL_METHOD_WRAPPER_FUN: Lazy<ObjRef<NativeFun>> = Lazy::new(|| {
 //
 // struct UserFun
 //
+
+pub type UserFunRef = ObjRef<UserFun>;
+
 #[derive(Scan)]
 pub struct UserFun {
     vtable: Vtable,