iconbutton: Cache icon surface instead of doing serveral hashtable lookups per

frame

src/iconbutton.h

@@ -7,6 +7,7 @@
 using std::string;
 
 class GMenu2X;
+class Surface;
 
 class IconButton : public Button {
 protected:
@@ -16,6 +17,10 @@ protected:
 	void recalcSize();
 	SDL_Rect iconRect, labelRect;
 
+	Surface *iconSurface;
+
+	void updateSurfaces();
+
 public:
 	static const int DISP_RIGHT = 0;
 	static const int DISP_LEFT = 1;