gsdx ogl: mark OGL object as final

Give the compiler more devirtualization hint

plugins/GSdx/GSDeviceOGL.h

@@ -114,7 +114,7 @@ public:
 	bool IsMaskEnable() { return m_depth_mask != GL_FALSE; }
 };
 
-class GSDeviceOGL : public GSDevice
+class GSDeviceOGL final : public GSDevice
 {
 	public:
 	__aligned(struct, 32) VSConstantBuffer

plugins/GSdx/GSRendererOGL.h

@@ -27,7 +27,7 @@
 #include "GSTextureCacheOGL.h"
 #include "GSVertexHW.h"
 
-class GSRendererOGL : public GSRendererHW
+class GSRendererOGL final : public GSRendererHW
 {
 	enum PRIM_OVERLAP {
 		PRIM_OVERLAP_UNKNOW,

plugins/GSdx/GSTextureCacheOGL.h

@@ -25,7 +25,7 @@
 #include "GSTextureCache.h"
 #include "GSDeviceOGL.h"
 
-class GSTextureCacheOGL : public GSTextureCache
+class GSTextureCacheOGL final : public GSTextureCache
 {
 protected:
 	int Get8bitFormat() { return GL_R8;}

plugins/GSdx/GSTextureOGL.h

@@ -38,7 +38,7 @@ namespace PboPool {
 	void Destroy();
 }
 
-class GSTextureOGL : public GSTexture
+class GSTextureOGL final : public GSTexture
 {
 	private:
 		GLuint m_texture_id;	 // the texture id

plugins/GSdx/GSWndOGL.h

@@ -25,7 +25,7 @@
 #include <X11/Xlib.h>
 #include <GL/glx.h>
 
-class GSWndOGL : public GSWndGL
+class GSWndOGL final : public GSWndGL
 {
 	Window     m_NativeWindow;
 	Display*   m_NativeDisplay;