Adapt to 4.9

Change-Id: I9c413eaf6d70eaf09640aed349c876c040ef55ba
Reviewed-by: Orgad Shaneh <orgads@gmail.com>

plugins/fossil/fossilcommitwidget.h

@@ -59,7 +59,7 @@ public:
     bool isPrivateOptionEnabled() const;
 
 protected:
-    bool canSubmit() const;
+    bool canSubmit(QString *whyNot = nullptr) const;
 
 private slots:
     void branchChanged();