DiffEditor: Modernize

* Use member init
* Use nullptr
* Use range-for
* omit QLatin1{String|Char} where possible

Change-Id: Ib231b747cdd9073b3d4fc6779b8e0afb2b404a31
Reviewed-by: Orgad Shaneh <orgads@gmail.com>
Reviewed-by: André Hartmann <aha_1980@gmx.de>

src/plugins/diffeditor/diffview.h

@@ -50,7 +50,7 @@ class IDiffView : public QObject
     Q_OBJECT
 
 public:
-    explicit IDiffView(QObject *parent = 0);
+    explicit IDiffView(QObject *parent = nullptr);
 
     QIcon icon() const;
     QString toolTip() const;
@@ -82,7 +82,7 @@ private:
     QIcon m_icon;
     QString m_toolTip;
     Core::Id m_id;
-    bool m_supportsSync;
+    bool m_supportsSync = false;
     QString m_syncToolTip;
 };