Unordered: Remove malloc_allocator.

It was originally introduced because of some issues with Boost.Test and older
compilers, neither of which I'm using now. Simplifies a few things.

[SVN r79352]

test/helpers/invariants.hpp

@@ -13,7 +13,6 @@
 #include <cmath>
 #include "./metafunctions.hpp"
 #include "./helpers.hpp"
-#include "./allocator.hpp"
 
 #if defined(BOOST_MSVC)
 #pragma warning(push)
@@ -29,10 +28,7 @@ namespace test
     {
         BOOST_DEDUCED_TYPENAME X::key_equal eq = x1.key_eq();
         typedef BOOST_DEDUCED_TYPENAME X::key_type key_type;
-        // Boost.Test was reporting memory leaks for std::set on g++-3.3.
-        // So I work around it by using malloc.
-        std::set<key_type, std::less<key_type>,
-            test::malloc_allocator<key_type> > found_;
+        std::set<key_type, std::less<key_type> > found_;
 
         BOOST_DEDUCED_TYPENAME X::const_iterator
             it = x1.begin(), end = x1.end();