Make hezrous stink

src/mon.c

@@ -145,9 +145,9 @@ struct monst *mtmp;
     int px, py;
     boolean is_you = (mtmp == &g.youmonst);
 
-    /* Non living and non breathing monsters are not concerned */
+    /* Non living, non breathing, immune monsters are not concerned */
     if (nonliving(mtmp->data) || is_vampshifter(mtmp)
-        || breathless(mtmp->data))
+        || breathless(mtmp->data) || immune_poisongas(mtmp->data))
         return M_POISONGAS_OK;
     /* not is_swimmer(); assume that non-fish are swimming on
        the surface and breathing the air above it periodically

src/monmove.c

@@ -623,6 +623,9 @@ register struct monst *mtmp;
     /*  Now the actual movement phase
      */
 
+    if (mtmp->data == &mons[PM_HEZROU]) /* stench */
+        create_gas_cloud(mtmp->mx, mtmp->my, 1, 8);
+
     if (mdat == &mons[PM_KILLER_BEE]
         /* could be smarter and deliberately move to royal jelly, but
            then we'd need to scan the level for queen bee in advance;