Style: Fixup instances of void arguments

The style we have here is that functions with no arguments are to have
explicit `void` arguments, even though this doesn't apply in C++,
because it does apply in C.

Unfortunately, some have slipped through the cracks. This commit fixes
them.

desktop_version/src/Screen.h

@@ -19,7 +19,7 @@ public:
     void ResizeToNearestMultiple(void);
     void GetWindowSize(int* x, int* y);
 
-    void RenderPresent();
+    void RenderPresent(void);
 
     void toggleFullScreen(void);
     void toggleScalingMode(void);