Introduced CPlusPlus::Snapshot, it contains a snap shot of the indexer's current state.

This change removes a number of wrong usages of the CppModelManager::documents()/document().

src/libs/cplusplus/CppDocument.h

@@ -40,7 +40,7 @@
 
 #include <QByteArray>
 #include <QList>
-#include <QSet>
+#include <QMap>
 #include <QSharedPointer>
 #include <QString>
 #include <QStringList>
@@ -236,6 +236,16 @@ private:
     QList<MacroUse> _macroUses;
 };
 
+class CPLUSPLUS_EXPORT Snapshot: public QMap<QString, Document::Ptr>
+{
+public:
+    Snapshot()
+    { }
+
+    ~Snapshot()
+    { }
+};
+
 } // end of namespace CPlusPlus
 
 #endif // CPPDOCUMENT_H