logical update semantics:

instance of erased element should fail;
  garbage collection now tries to recover space for code.


git-svn-id: https://yap.svn.sf.net/svnroot/yap/trunk@512 b08c6af1-5177-4d33-ba66-4b1c6b8b522a

C/save.c

@@ -1158,6 +1158,8 @@ restore_codes(void)
 #endif
   if (heap_regs->last_wtime != NULL)
     heap_regs->last_wtime = (void *)PtoHeapCellAdjust((CELL *)(heap_regs->last_wtime));
+  heap_regs->db_erased_marker =
+    DBRefAdjust(heap_regs->db_erased_marker);
 }
 
 /* restore some heap registers */