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/vm/inst.rs

@@ -1,6 +1,6 @@
 use crate::{obj::prelude::*, vm::consts::ConstHandle};
 
-#[derive(Debug, PartialEq)]
+#[derive(Debug, PartialEq, Clone, Copy)]
 pub enum Inst {
     /// Push a literal symbol object to the stack.
     PushSym(Sym),