Combine most of the detail headers into a single header

test/helpers/memory.hpp

@@ -9,7 +9,7 @@
 #include <memory>
 #include <map>
 #include <boost/assert.hpp>
-#include <boost/unordered/detail/allocate.hpp>
+#include <boost/unordered/detail/implementation.hpp>
 #include "../helpers/test.hpp"
 
 namespace test