Refactoring changes: Cleanup and improvements.

Previously RefactoringFiles were usually passed around by value.
However, since a RefactoringFile may sometimes own a QTextDocument
(when it was read from a file), that's not great and caused the
file to be reread after every copy.

With this change RefactoringFile becomes noncopyable and is always
owned by a shared pointer.

This change also allowed having const RefactoringFiles which is
useful because they can be safely used from other threads. See
CppRefactoringChanges::fileNoEditor.

Change-Id: I9045921d6d0f6349f9558ff2a3d8317ea172193b
Reviewed-on: http://codereview.qt.nokia.com/3084
Reviewed-by: Leandro T. C. Melo <leandro.melo@nokia.com>

src/plugins/cppeditor/cppquickfix.h

@@ -40,6 +40,7 @@ namespace CppTools {
     class CppModelManagerInterface;
     class CppRefactoringFile;
     class CppRefactoringChanges;
+    typedef QSharedPointer<CppRefactoringFile> CppRefactoringFilePtr;
 } // namespace CppTools
 
 namespace ExtensionSystem {
@@ -63,8 +64,8 @@ public:
     virtual void perform();
 
 protected:
-    virtual void performChanges(CppTools::CppRefactoringFile *currentFile,
-                                CppTools::CppRefactoringChanges *refactoring) = 0;
+    virtual void performChanges(const CppTools::CppRefactoringFilePtr &currentFile,
+                                const CppTools::CppRefactoringChanges &refactoring) = 0;
 
     QString fileName() const;