Strip c-style void in function defs

This was never needed for c++.

src/gnudiff_diff.h

@@ -217,7 +217,7 @@ class GnuDiff
     // gnudiff_xmalloc.cpp
     void *xmalloc(size_t n);
     void *xrealloc(void *p, size_t n);
-    void xalloc_die(void);
+    void xalloc_die();
 
     inline bool isWhite(QChar c)
     {

src/gnudiff_xmalloc.cpp

@@ -30,9 +30,9 @@
 
 #include "gnudiff_diff.h"
 /* If non NULL, call this function when memory is exhausted. */
-void (*xalloc_fail_func)(void) = nullptr;
+void (*xalloc_fail_func)() = nullptr;
 
-void GnuDiff::xalloc_die(void)
+void GnuDiff::xalloc_die()
 {
     if(xalloc_fail_func)
         (*xalloc_fail_func)();

src/optiondialog.h

@@ -47,7 +47,7 @@ class OptionDialog : public KPageDialog
 public:
 
     explicit OptionDialog( bool bShowDirMergeSettings, QWidget *parent = nullptr );
-    ~OptionDialog( void ) override;
+    ~OptionDialog() override;
     QString parseOptions( const QStringList& optionList );
     QString calcOptionHelp();
 
@@ -61,9 +61,9 @@ public:
     void addOptionItem(OptionItemBase*);
     KKeyDialog* m_pKeyDialog;
 protected Q_SLOTS:
-    virtual void slotDefault( void );
-    virtual void slotOk( void );
-    virtual void slotApply( void );
+    virtual void slotDefault();
+    virtual void slotOk();
+    virtual void slotApply();
     //virtual void buttonClicked( QAbstractButton* );
     virtual void helpRequested();