implement iseq, tests

Signed-off-by: Ava Hahn <ava@aidanis.online>

src/stl.rs

@@ -100,16 +100,6 @@ pub fn static_stdlib(syms: &mut SymTable) -> Result<(), String> {
         }
     );
 
-    syms.insert(
-        "xor".to_string(),
-        Symbol {
-            name: String::from("xor"),
-            args: Args::Infinite,
-            conditional_branches: false,
-            value: ValueType::Internal(Rc::new(boolean::bool_xor_callback)),
-        }
-    );
-
     syms.insert(
         "not".to_string(),
         Symbol {