Saving grace

Once per game, if receiving a killing blow from above 90% HP,
allow the hero to survive with 1 HP.

include/extern.h

@@ -987,6 +987,7 @@ extern int monster_nearby(void);
 extern void end_running(boolean);
 extern void nomul(int);
 extern void unmul(const char *);
+extern int saving_grace(int);
 extern void losehp(int, const char *, schar);
 extern int weight_cap(void);
 extern int inv_weight(void);

include/patchlevel.h

@@ -17,7 +17,7 @@
  * Incrementing EDITLEVEL can be used to force invalidation of old bones
  * and save files.
  */
-#define EDITLEVEL 75
+#define EDITLEVEL 76
 
 /*
  * Development status possibilities.

include/you.h

@@ -419,7 +419,7 @@ struct you {
     Bitfield(uinvulnerable, 1); /* you're invulnerable (praying) */
     Bitfield(uburied, 1);       /* you're buried */
     Bitfield(uedibility, 1);    /* blessed food detect; sense unsafe food */
-    /* 1 free bit! */
+    Bitfield(usaving_grace, 1); /* prevents death once */
 
     unsigned udg_cnt;           /* how long you have been demigod */
     struct u_event uevent;      /* certain events have happened */