VideoBackends: Use vertex shader depth range if ztexture is used.

Source/Core/VideoCommon/RenderBase.h

@@ -145,6 +145,8 @@ public:
   // Final surface changing
   // This is called when the surface is resized (WX) or the window changes (Android).
   virtual void ChangeSurface(void* new_surface_handle) {}
+  bool UseVertexDepthRange() const;
+
 protected:
   static void CalculateTargetScale(int x, int y, int* scaledX, int* scaledY);
   bool CalculateTargetSize();