make the parsing stage pass even if non-defaultable items have been defaulted

... but throw later when trying to access the data of the item in
question.

Note that this was demanded by [at] joakim-hove and that I do not want
to be held responsible for any issues which are caused by this
approach. (read: please direct your barks to Joakim if you fell on
your nose because of this...)

opm/parser/eclipse/Deck/DeckIntItem.cpp

@@ -35,6 +35,9 @@ namespace Opm {
     }
 
     void DeckIntItem::push_back(std::deque<int> data, size_t items) {
+        if (m_dataPointDefaulted.size() != m_data.size())
+            throw std::logic_error("To add a value to an item, no \"pseudo defaults\" can be added before");
+
         for (size_t i = 0; i < items; i++) {
             m_data.push_back(data[i]);
             m_dataPointDefaulted.push_back(false);
@@ -42,21 +45,40 @@ namespace Opm {
     }
 
     void DeckIntItem::push_back(std::deque<int> data) {
+        if (m_dataPointDefaulted.size() != m_data.size())
+            throw std::logic_error("To add a value to an item, no \"pseudo defaults\" can be added before");
+
         push_back(data, data.size());
         m_dataPointDefaulted.push_back(false);
     }
 
     void DeckIntItem::push_back(int data) {
+        if (m_dataPointDefaulted.size() != m_data.size())
+            throw std::logic_error("To add a value to an item, no \"pseudo defaults\" can be added before");
+
         m_data.push_back(data);
         m_dataPointDefaulted.push_back(false);
     }
 
     void DeckIntItem::push_backDefault(int data) {
+        if (m_dataPointDefaulted.size() != m_data.size())
+            throw std::logic_error("To add a value to an item, no \"pseudo defaults\" can be added before");
+
         m_data.push_back( data );
         m_dataPointDefaulted.push_back(true);
     }
 
+    void DeckIntItem::push_backDummyDefault() {
+        if (m_dataPointDefaulted.size() != 0)
+            throw std::logic_error("Pseudo defaults can only be specified for empty items");
+
+        m_dataPointDefaulted.push_back(true);
+    }
+
     void DeckIntItem::push_backMultiple(int value, size_t numValues) {
+        if (m_dataPointDefaulted.size() != m_data.size())
+            throw std::logic_error("To add a value to an item, no \"pseudo defaults\" can be added before");
+
         for (size_t i = 0; i < numValues; i++) {
             m_data.push_back( value );
             m_dataPointDefaulted.push_back(false);