Add invocation queue to DrivenEngine, use it for lua source

luprex/cpp/core/invocation.hpp

@@ -40,11 +40,10 @@
 #include "wrap-string.hpp"
 #include "wrap-map.hpp"
 #include "wrap-deque.hpp"
-
 #include "streambuffer.hpp"
 
 
-class Invocation : public eng::nevernew {
+class Invocation : public eng::opnew {
 public:
     enum Kind {
         KIND_INVALID,
@@ -76,6 +75,8 @@ public:
     eng::string debug_string() const;
 };
 
+using UniqueInvocation = std::unique_ptr<Invocation>;
+
 class InvocationQueue : public eng::deque<Invocation> {
 };