Add boolean option "bones"

Setting bones off prevents saving and loading bones files.

include/flag.h

@@ -21,6 +21,7 @@ struct flag {
 	boolean  autoquiver;	/* Automatically fill quiver */
 	boolean  beginner;
 	boolean  biff;		/* enable checking for mail */
+	boolean  bones;		/* allow saving/loading bones */
 	boolean  confirm;	/* confirm before hitting tame monsters */
 	boolean  debug;		/* in debugging mode */
 #define wizard	 flags.debug

include/patchlevel.h

@@ -14,7 +14,7 @@
  * Incrementing EDITLEVEL can be used to force invalidation of old bones
  * and save files.
  */
-#define EDITLEVEL	55
+#define EDITLEVEL	56
 
 #define COPYRIGHT_BANNER_A \
 "NetHack, Copyright 1985-2012"