OLD1 ages advanced by 'markold'

Objects aged OLD1 have their ages advanced by 'markold', which has to
visit them anyway. So, the GC doesn't need to "sweep" the old1 list.

lgc.c

@@ -1131,7 +1131,7 @@ static void correctgraylists (global_State *g) {
 
 
 /*
-** Mark 'OLD1' objects when starting a new young collection.
+** Mark black 'OLD1' objects when starting a new young collection.
 ** Gray objects are already in some gray list, and so will be visited
 ** in the atomic step.
 */
@@ -1140,6 +1140,7 @@ static void markold (global_State *g, GCObject *from, GCObject *to) {
   for (p = from; p != to; p = p->next) {
     if (getage(p) == G_OLD1) {
       lua_assert(!iswhite(p));
+      changeage(p, G_OLD1, G_OLD);  /* now they are old */
       if (isblack(p)) {
         black2gray(p);  /* should be '2white', but gray works too */
         reallymarkobject(g, p);
@@ -1176,16 +1177,16 @@ static void youngcollection (lua_State *L, global_State *g) {
   /* sweep nursery and get a pointer to its last live element */
   g->gcstate = GCSswpallgc;
   psurvival = sweepgen(L, g, &g->allgc, g->survival);
-  /* sweep 'survival' and 'old' */
+  /* sweep 'survival' */
-  sweepgen(L, g, psurvival, g->reallyold);
+  sweepgen(L, g, psurvival, g->old);
   g->reallyold = g->old;
   g->old = *psurvival;  /* 'survival' survivals are old now */
   g->survival = g->allgc;  /* all news are survivals */
 
   /* repeat for 'finobj' lists */
   psurvival = sweepgen(L, g, &g->finobj, g->finobjsur);
-  /* sweep 'survival' and 'old' */
+  /* sweep 'survival' */
-  sweepgen(L, g, psurvival, g->finobjrold);
+  sweepgen(L, g, psurvival, g->finobjold);
   g->finobjrold = g->finobjold;
   g->finobjold = *psurvival;  /* 'survival' survivals are old now */
   g->finobjsur = g->finobj;  /* all news are survivals */