fix crash in 997: re-introduce cfindhash.

this prevents duplicate curse.no values.

src/kernel/curse.c

@@ -98,6 +98,15 @@ static void cunhash(curse * c)
     }
 }
 
+curse *cfindhash(int i)
+{
+    curse *old;
+
+    for (old = cursehash[i % MAXENTITYHASH]; old; old = old->nexthash)
+        if (old->no == i)
+            return old;
+    return NULL;
+}
 /* ------------------------------------------------------------- */
 /* at_curse */
 void curse_init(attrib * a)

src/kernel/curse.h

@@ -285,6 +285,7 @@ extern "C" {
     void ct_register(const curse_type *);
     void ct_checknames(void);
 
+    curse *cfindhash(int i);
     curse *findcurse(int curseid);
 
     void curse_init(struct attrib *a);

src/kernel/unit.c

@@ -1876,6 +1876,7 @@ int newunitid(void)
     start_random_no = random_unit_no;
 
     while (ufindhash(random_unit_no) || dfindhash(random_unit_no)
+        || cfindhash(random_unit_no)
         || forbiddenid(random_unit_no)) {
         random_unit_no++;
         if (random_unit_no == MAX_UNIT_NR + 1) {