Ensure that the memory pool can be reused after a rewind and get rid of the segmented array.

src/libs/cplusplus/CppDocument.h

@@ -86,7 +86,9 @@ public:
     unsigned globalSymbolCount() const;
     Symbol *globalSymbolAt(unsigned index) const;
     Scope *globalSymbols() const; // ### deprecate?
+
     Namespace *globalNamespace() const;
+    void setGlobalNamespace(Namespace *globalNamespace); // ### internal
 
     QList<Macro> definedMacros() const
     { return _definedMacros; }