repair for locked-object handling and multiply-locked values

Weak pairs, ephemeron pairs, some symbols, and some ports were handled
incorerctly when locked multiple times.

original commit: 847fc1c84496f67cd363c8411d0023339f4d6246

c/gc.c

@@ -2213,8 +2213,10 @@ static void sanitize_locked_segment(seginfo *si) {
     /* Zero out unused memory */
     while (pp < ppend) {
       if ((ls != Snil) && (pp == UNTYPE_ANY(Scar(ls)))) {
+        ptr a = Scar(ls);
         pp = (ptr *)((uptr)pp + size_object(Scar(ls)));
-        ls = Scdr(ls);
+        while ((ls != Snil) && (Scar(ls) == a))
+          ls = Scdr(ls);
       } else {
         *pp = FIX(0);
         pp++;

mats/misc.ms

@@ -3562,6 +3562,7 @@
       (vector-set! v (sub1 N) p)
       (collect 0)
       (set-car! p 'yes)
+      (unlock-object v)
       (equal? '(yes . 2) (vector-ref v (sub1 N)))))
 )