DiffEditor: Pimpl plugin

The standard pattern, and allows to drop the QObject parent on
the editor factory which gets into the way of de-QObject-ifing
the IEditorFactory hierarchy.

Change-Id: I5c6a50f8075a99592ed4459b417ca8ba7471ae96
Reviewed-by: Christian Stenger <christian.stenger@qt.io>

src/plugins/diffeditor/diffeditorfactory.cpp

@@ -36,8 +36,7 @@
 namespace DiffEditor {
 namespace Internal {
 
-DiffEditorFactory::DiffEditorFactory(QObject *parent)
-    : IEditorFactory(parent)
+DiffEditorFactory::DiffEditorFactory()
 {
     setId(Constants::DIFF_EDITOR_ID);
     setDisplayName(QCoreApplication::translate("DiffEditorFactory", Constants::DIFF_EDITOR_DISPLAY_NAME));