Fixed a deadlock in free_unreachable_objects.

[SVN r17090]

src/sp_collector.cpp

@@ -194,6 +194,9 @@ static void scan_and_free(void * area, size_t size, map2_type const & m2, free_l
 }
 
 void free_unreachable_objects()
+{
+    free_list_type free;
+
     {
         map2_type m2;
 
@@ -207,14 +210,13 @@ void free_unreachable_objects()
 
         find_unreachable_objects_impl(m, m2);
 
-    free_list_type free;
-
         for(map2_type::iterator j = m2.begin(); j != m2.end(); ++j)
         {
             map_type::const_iterator i = m.find(j->first);
             BOOST_ASSERT(i != m.end());
             scan_and_free(i->second.first, i->second.second, m2, free);
         }
+    }
 
     std::cout << "... about to free " << free.size() << " objects.\n";
 }