Hide plastic babies in slices of king cake

Sometimes the hero will find a plastic baby inside a piece of king cake,
just like in real life.

In order to make this apply to 'real' king cake created during Mardi
Gras, and not to user-defined fruit with an identical name, change
holiday fruits to use a negative fruit ID as their spe. To enable this,
add a new macro, fruit_id() -- which provides the absolute value of
fruit->spe -- and use it in most cases the fruit ID needs to be
accessed.

Negative fruit IDs are already used when saving bones, to mark fruits
which don't exist on the current level and therefore don't need to be
included in the bones file, but those are negative fids in the g.ffruit
linked list, not negative spe on individual items.  These changes
shouldn't interfere with that process as long as the possible negative
spe is taken into consideration when saving and loading bones, which it
now should be.

include/obj.h

@@ -476,6 +476,11 @@ struct obj {
 #define thiefstone_ledger_valid(stone) \
     ((stone)->keyed_ledger > 0 && (stone)->keyed_ledger <= maxledgerno())
 
+/* special holiday fruits are differentiated from user-defined fruits by
+ * negative spe */
+#define is_holiday_fruit(obj) ((obj)->otyp == SLIME_MOLD && (obj)->spe < 0)
+#define fruit_id(obj) (abs((obj)->spe))
+
 /*
  *  Notes for adding new oextra structures:
  *

src/bones.c

@@ -137,7 +137,7 @@ resetobjs(struct obj *ochain, boolean restore)
             }
 
             if (otmp->otyp == SLIME_MOLD) {
-                goodfruit(otmp->spe);
+                goodfruit(fruit_id(otmp));
 #ifdef MAIL_STRUCTURES
             } else if (otmp->otyp == SCR_MAIL) {
                 /* 0: delivered in-game via external event;
@@ -321,7 +321,7 @@ drop_upon_death(struct monst *mtmp, /* monster if hero turned into one (other th
         otmp->owt = weight(otmp);
 
         if (otmp->otyp == SLIME_MOLD)
-            goodfruit(otmp->spe);
+            goodfruit(fruit_id(otmp));
 
         if (rn2(5))
             curse(otmp);

src/eat.c

@@ -2385,6 +2385,34 @@ fpostfx(struct obj *otmp)
             if (!u.uconduct.literate++)
                 livelog_printf(LL_CONDUCT, "became literate by reading the fortune inside a cookie");
         break;
+    case SLIME_MOLD: 
+        if (is_holiday_fruit(otmp)) {
+            struct fruit *f = fruit_from_indx(fruit_id(otmp));
+            if (!rn2(15) && f && !strcmp("slice of king cake", f->fname)) {
+                static const int babies[] = {
+                    PM_BABY_CROCODILE,
+                    PM_BABY_LONG_WORM,
+                    PM_BABY_PURPLE_WORM,
+                    PM_BABY_GRAY_DRAGON,
+                    PM_BABY_GOLD_DRAGON,
+                    PM_BABY_SILVER_DRAGON,
+                    PM_BABY_RED_DRAGON,
+                    PM_BABY_WHITE_DRAGON,
+                    PM_BABY_ORANGE_DRAGON,
+                    PM_BABY_BLACK_DRAGON,
+                    PM_BABY_BLUE_DRAGON,
+                    PM_BABY_GREEN_DRAGON,
+                    PM_BABY_YELLOW_DRAGON,
+                };
+                struct obj *feve = mksobj(FIGURINE, TRUE, FALSE);
+                set_corpsenm(feve, babies[rn2(SIZE(babies))]);
+                set_material(feve, PLASTIC);
+                There("is a plastic baby inside the slice of king cake!");
+                hold_another_object(feve, "It falls to the floor.",
+                                    (const char *) 0, (const char *) 0);
+            }
+        }
+        break;
     case LUMP_OF_ROYAL_JELLY:
         /* This stuff seems to be VERY healthy! */
         gainstr(otmp, 1, TRUE); /* will -1 if cursed */

src/mkobj.c

@@ -990,7 +990,8 @@ mksobj(int otyp, boolean init, boolean artif)
                         /* fruitadd requires a modifiable string */
                         char foodbuf[BUFSZ];
                         Strcpy(foodbuf, foods[rn2(idx)]);
-                        otmp->spe = fruitadd(foodbuf, NULL);
+                        /* holiday fruits have negative spe */
+                        otmp->spe = -fruitadd(foodbuf, NULL);
                     }
                 }
                 flags.made_fruit = TRUE;

src/objnam.c

@@ -631,7 +631,7 @@ xname_flags(
     case FOOD_CLASS:
         /* we could include partly-eaten-hack on fruit but don't need to */
         if (typ == SLIME_MOLD) {
-            struct fruit *f = fruit_from_indx(obj->spe);
+            struct fruit *f = fruit_from_indx(fruit_id(obj));
 
             if (!f) {
                 impossible("Bad fruit #%d?", obj->spe);

src/options.c

@@ -7172,7 +7172,7 @@ fruitadd(char *str, struct fruit *replace_fruit)
     char buf[PL_FSIZ], altname[PL_FSIZ];
     boolean user_specified = (str == g.pl_fruit);
     /* if not user-specified, then it's a fruit name for a fruit on
-     * a bones level or from orctown raider's loot...
+     * a bones level, a holiday food, or from orctown raider's loot...
      */
 
     /* Note: every fruit has an id (kept in obj->spe) of at least 1;

src/restore.c

@@ -507,13 +507,18 @@ ghostfruit(register struct obj* otmp)
     register struct fruit *oldf;
 
     for (oldf = g.oldfruit; oldf; oldf = oldf->nextf)
-        if (oldf->fid == otmp->spe)
+        if (oldf->fid == fruit_id(otmp))
             break;
 
-    if (!oldf)
+    if (!oldf) {
         impossible("no old fruit?");
-    else
+    } else {
+        boolean holiday_food = is_holiday_fruit(otmp);
         otmp->spe = fruitadd(oldf->fname, (struct fruit *) 0);
+        if (holiday_food) {
+            otmp->spe = -(otmp->spe);
+        }
+    }
 }
 
 #ifdef SYSCF