stoning resistance revisited

It turns out that there were a bunch more monsters with the corpse-
conveys-stoning-resistance flag than just green mold.  Instead of
stripping it off, give them (including green mold) a chance to confer
timed resistance against stoning and also against acid.

All of these can convey either of those two resistances.  Like other
intrinsics obtained via eating, at most one can be obtained from any
given corpse.
  green mold, acid blob, spotted jelly, ochre jelly, black naga,
  yellow dragon, Chromatic Dragon
These can confer temporary stoning resistance but not acid resistance:
  lizard, chickatrice, cockatrice, gargoyle, winged gargoyle,
  xorn, Medusa
There aren't any that confer just acid resistance without a chance for
stoning resistance.

The effect lasts for 3d6 turns, or is extended by 3d6 more if randomly
chosen and applied when already in effect.

Having temporary acid resistance time out during another meal when
eating a corpse that ends up conferring acid resistance seems strange.
The protection against acid is granted at the start of the meal and
continues to the end (in regards to eating, not external attacks) even
when the intrinisic is lost in between.  I'm not sure whether that
needs some form of fixing, and if so, what that fixing should be.

src/eat.c

@@ -1,4 +1,4 @@
-/* NetHack 3.7	eat.c	$NHDT-Date: 1647133629 2022/03/13 01:07:09 $  $NHDT-Branch: NetHack-3.7 $:$NHDT-Revision: 1.262 $ */
+/* NetHack 3.7	eat.c	$NHDT-Date: 1648318981 2022/03/26 18:23:01 $  $NHDT-Branch: NetHack-3.7 $:$NHDT-Revision: 1.269 $ */
 /* Copyright (c) Stichting Mathematisch Centrum, Amsterdam, 1985. */
 /*-Copyright (c) Robert Patrick Rankin, 2012. */
 /* NetHack may be freely redistributed.  See license for details. */
@@ -19,6 +19,7 @@ static void do_reset_eat(void);
 static void done_eating(boolean);
 static void cprefx(int);
 static int intrinsic_possible(int, struct permonst *);
+static boolean temp_givit(int, struct permonst *);
 static void givit(int, struct permonst *);
 static void eye_of_newt_buzz(void);
 static void cpostfx(int);
@@ -326,7 +327,7 @@ touchfood(struct obj *otmp)
             (void) splitobj(otmp, otmp->quan - 1L);
         else
             otmp = splitobj(otmp, 1L);
-        debugpline0("split object,");
+        debugpline0("split food,");
     }
 
     if (!otmp->oeaten) {
@@ -761,7 +762,7 @@ fix_petrification(void)
 
 /* intrinsic_possible() returns TRUE iff a monster can give an intrinsic. */
 static int
-intrinsic_possible(int type, register struct permonst *ptr)
+intrinsic_possible(int type, struct permonst *ptr)
 {
     int res = 0;
 
@@ -799,6 +800,14 @@ intrinsic_possible(int type, register struct permonst *ptr)
         res = (ptr->mconveys & MR_POISON) != 0;
         ifdebugresist("can get poison resistance");
         break;
+    case ACID_RES:
+        res = (ptr->mconveys & MR_ACID) != 0;
+        ifdebugresist("can get acid resistance temporarily");
+        break;
+    case STONE_RES:
+        res = (ptr->mconveys & MR_STONE) != 0;
+        ifdebugresist("can get stoning resistance temporarily");
+        break;
     case TELEPORT:
         res = can_teleport(ptr);
         ifdebugresist("can get teleport");
@@ -854,6 +863,14 @@ should_givit(int type, struct permonst *ptr)
     return (ptr->mlevel > rn2(chance));
 }
 
+static boolean
+temp_givit(int type, struct permonst *ptr)
+{
+    int chance = (type == STONE_RES) ? 6 : (type == ACID_RES) ? 3 : 0;
+
+    return chance ? (ptr->mlevel > rn2(chance)) : FALSE;
+}
+
 /* givit() tries to give you an intrinsic based on the monster's level
  * and what type of intrinsic it is trying to give you.
  */
@@ -862,7 +879,7 @@ givit(int type, register struct permonst *ptr)
 {
     debugpline1("Attempting to give intrinsic %d", type);
 
-    if (!should_givit(type, ptr))
+    if (!should_givit(type, ptr) && !temp_givit(type, ptr))
         return;
 
     switch (type) {
@@ -937,14 +954,26 @@ givit(int type, register struct permonst *ptr)
                 see_monsters();
         }
         break;
+    case ACID_RES:
+        debugpline0("Giving timed acid resistance");
+        if (!Acid_resistance)
+            You_feel("%s.", Hallucination ? "secure from flashbacks"
+                            : "less concerned about being harmed by acid");
+        incr_itimeout(&HAcid_resistance, d(3, 6));
+        break;
+    case STONE_RES:
+        debugpline0("Giving timed stoning resistance");
+        if (!Stone_resistance)
+            You_feel("%s.", Hallucination ? "unusually limber"
+                            : "less concerned about becoming pertrified");
+        incr_itimeout(&HStone_resistance, d(3, 6));
+        break;
     default:
         debugpline0("Tried to give an impossible intrinsic");
         break;
     }
 }
 
-DISABLE_WARNING_FORMAT_NONLITERAL
-
 static void
 eye_of_newt_buzz(void)
 {
@@ -968,6 +997,8 @@ eye_of_newt_buzz(void)
     }
 }
 
+DISABLE_WARNING_FORMAT_NONLITERAL
+
 /* called after completely consuming a corpse */
 static void
 cpostfx(int pm)
@@ -1078,6 +1109,7 @@ cpostfx(int pm)
             make_stunned(2L, FALSE);
         if ((HConfusion & TIMEOUT) > 2)
             make_confused(2L, FALSE);
+        check_intrinsics = TRUE; /* might convery temporary stoning resist */
         break;
     case PM_CHAMELEON:
     case PM_DOPPELGANGER: