Ask the cell itself whether its command is still pending, guard the order table

The spent command was tracked in a table flag, which is lost whenever the speed
table is rebuilt - the cell would go back to being a stop point. The memcell
already knows: StopCommandSent() drops the pending flag and keeps the text, so
the event now answers is_command_spent() and the table point follows it.

OrderNextGet() read one past the end of OrderList when the current order sat in
the last slot; it now reports Wait_for_orders there, which is what OrderNext()
wraps to anyway.

world/Event.cpp

@@ -415,6 +415,13 @@ basic_event::is_command() const {
     return false;
 };
 
+// returns: true for a data cell whose command has already been delivered
+bool
+basic_event::is_command_spent() const {
+
+    return false;
+};
+
 std::string
 basic_event::input_text() const {
     // odczytanie komendy z eventu
@@ -650,6 +657,13 @@ getvalues_event::is_command() const {
     return m_input.data_cell()->StopCommand();
 }
 
+// returns: true for a data cell whose command has already been delivered
+bool
+getvalues_event::is_command_spent() const {
+    // the cell keeps its text after the command was sent, only the pending flag is dropped
+    return false == m_input.data_cell()->StopCommand();
+}
+
 // input data access
 std::string
 getvalues_event::input_text() const {