fix issue #1061 - dipping container into water

Issue reported by loggersviii:  dipping a container into an uncursed
potion of water mentions water getting into the container.  That
happens even when that type of potion hasn't been discovered yet.

Make POT_WATER become discovered if this occurs.  Doesn't apply when
hallucinating where a random liquid is mentioned instead of water.

Fixes #1061

src/decl.c

@@ -551,6 +551,8 @@ const struct instance_globals_m g_init_m = {
     UNDEFINED_VALUES, /* mapped_menu_op */
     /* region.c */
     0, /* max_regions */
+    /* trap.c */
+    FALSE, /* mentioned_water */
     TRUE, /* havestate*/
     IVMAGIC  /* m_magic to validate that structure layout has been preserved */
 };

src/potion.c

@@ -1512,8 +1512,12 @@ H2Opotion_dip(
     } else {
         /* dipping into uncursed water; carried() check skips steed saddle */
         if (carried(targobj)) {
+            gm.mentioned_water = FALSE; /* water_damage() might set this */
             if (water_damage(targobj, 0, TRUE) != ER_NOTHING)
                 res = TRUE;
+            if (gm.mentioned_water)
+                makeknown(POT_WATER);
+            gm.mentioned_water = FALSE;
         }
     }
     if (func) {

src/trap.c

@@ -4208,8 +4208,7 @@ acid_damage(struct obj* obj)
 
 /* Get an object wet and damage it appropriately.
  *   "obj": if null, returns ER_NOTHING
- *   "ostr", if present, is used instead of the object name in some
- *     messages.
+ *   "ostr", if present, is used instead of the object name in some messages.
  *   "force" means not to roll luck to protect some objects.
  * Returns an erosion return value (ER_*)
  */
@@ -4253,14 +4252,18 @@ water_damage(
         return ER_GREASED;
     } else if (Is_container(obj)
                && (!Waterproof_container(obj) || (obj->cursed && !rn2(3)))) {
-        if (in_invent)
+        if (in_invent) {
             pline("Some %s gets into your %s!", hliquid("water"), ostr);
+            gm.mentioned_water = !Hallucination;
+        }
         water_damage_chain(obj->cobj, FALSE);
         return ER_DAMAGED; /* contents were damaged */
     } else if (Waterproof_container(obj)) {
         if (in_invent) {
             pline_The("%s slides right off your %s.", hliquid("water"), ostr);
-            makeknown(obj->otyp);
+            gm.mentioned_water = !Hallucination;
+            makeknown(obj->otyp); /* if an oilskin sack, discover it; doesn't
+                                   * matter for chest, large box, ice box */
         }
         /* not actually damaged, but because we /didn't/ get the "water
            gets into!" message, the player now has more information and