Added definition of RETAIN RELEASE AUTORELEASE macros for ARC.

diff --git a/sources/Hangman.h b/sources/Hangman.h
index 82b3f9c..9f775cd 100644
--- a/sources/Hangman.h
+++ b/sources/Hangman.h
@@ -35,6 +35,11 @@
 #define Hangman_h
 #include <Foundation/Foundation.h>

+#if __has_feature(objc_arc)
+#define RETAIN(x) (x)
+#define RELEASE(x) (x)
+#define AUTORELEASE(x) (x)
+#endif

 typedef enum {
     Hangman_wins,