Removed "delegate.h"

The abstraction it provided was so thin that I think it is simpler to
just have the code use std::bind directly.

src/iconbutton.h

@@ -1,10 +1,11 @@
 #ifndef ICONBUTTON_H
 #define ICONBUTTON_H
 
-#include "delegate.h"
 #include "gmenu2x.h"
 
 #include <SDL.h>
+
+#include <functional>
 #include <string>
 
 class OffscreenSurface;
@@ -14,9 +15,11 @@ class Touchscreen;
 
 class IconButton {
 public:
+	typedef std::function<void(void)> Action;
+
 	IconButton(GMenu2X *gmenu2x, Touchscreen &ts,
 			const std::string &icon, const std::string &label = "",
-			function_t action = nullptr);
+			Action action = nullptr);
 
 	SDL_Rect getRect() { return rect; }
 	void setPosition(int x, int y);
@@ -31,7 +34,7 @@ private:
 	GMenu2X *gmenu2x;
 	Touchscreen &ts;
 	std::string icon, label;
-	function_t action;
+	Action action;
 
 	SDL_Rect rect, iconRect, labelRect;
 	OffscreenSurface *iconSurface;