Rename DiffEditorFile -> DiffEditorDocument

The old name had nothing to do with a file in fact.
The new name will be more appropriate for the new stuff,
which will come soon.

Change-Id: I17ad03dab5c643ff26e313a434ba86929a0f00c3
Reviewed-by: Eike Ziller <eike.ziller@digia.com>

src/plugins/diffeditor/diffeditor.h

@@ -45,7 +45,7 @@ namespace DiffEditor {
 class DiffEditorWidget;
 
 namespace Internal {
-class DiffEditorFile;
+class DiffEditorDocument;
 }
 
 class DIFFEDITOR_EXPORT DiffEditor : public Core::IEditor
@@ -80,7 +80,7 @@ protected:
 private:
     void updateEntryToolTip();
 
-    Internal::DiffEditorFile *m_file;
+    Internal::DiffEditorDocument *m_document;
     DiffEditorWidget *m_editorWidget;
     DiffEditorController *m_diffEditorController;
     QComboBox *m_entriesComboBox;