Added explicit 'void' to function that takes no argument

This is the correct way to tell that a function takes no
arguments, because an empty parameter list tells the compiler
that it is not yet defined, and is tolerated only for
compatibility with very old C compilers for whom prototypes
were not yet a defined language element.

src/winspector.h

@@ -30,7 +30,7 @@ void wHideInspectorForWindow(WWindow *wwin);
 
 void wUnhideInspectorForWindow(WWindow *wwin);
 
-void wDestroyInspectorPanels();
+void wDestroyInspectorPanels(void);
 
 WWindow *wGetWindowOfInspectorForWindow(WWindow *wwin);