Added MachineOk to one_instruction

src/simulator/error.rs

@@ -24,6 +24,11 @@ pub struct MachineError {
     message: String
 }
 
+pub enum MachineOk {
+    Ok,
+    Shutdown
+}
+
 /// This impl allows this MachineError to be formatted into an empty format.
 /// 
 /// ```