Wizards: Make it possible to check existing files to overwrite.

Present a checkable list of files to be overwritten,
enabling re-generating a part of the project or class.

Task-number: QTCREATORBUG-4538

src/plugins/coreplugin/basefilewizard.h

@@ -69,7 +69,9 @@ public:
                      OpenProjectAttribute = 0x02,
                      /* File is generated by external scripts, do not write out,
                       * see BaseFileWizard::writeFiles() */
-                     CustomGeneratorAttribute = 0x4
+                     CustomGeneratorAttribute = 0x4,
+                     /* File exists and the user indicated that he wants to keep it */
+                     KeepExistingFileAttribute = 0x8
                    };
     Q_DECLARE_FLAGS(Attributes, Attribute)
 
@@ -188,7 +190,7 @@ protected:
     static QString preferredSuffix(const QString &mimeType);
 
     enum OverwriteResult { OverwriteOk,  OverwriteError,  OverwriteCanceled };
-    OverwriteResult promptOverwrite(const QStringList &files,
+    OverwriteResult promptOverwrite(GeneratedFiles *files,
                                     QString *errorMessage) const;
     static bool postGenerateOpenEditors(const GeneratedFiles &l, QString *errorMessage = 0);