Unordered: Merge unordered from trunk.

- Activate `std::allocator_traits` for gcc 4.7 and Visual C++ 11.
- Implement variadic construct in `boost::unordered::detail::allocator_traits`
  when variadics, rvalue references and SFINAE expression are available.
- Use variadic construct from `allocator_traits`, or when not available move
  the logic for constructing `value_type` to a lower level, so the container
  code is a bit simpler.
- Avoid `-Wshadow` warnings. Fixes #6190.
- Implement `reserve`. Fixes #6857.


[SVN r78432]

test/helpers/list.hpp

@@ -219,14 +219,14 @@ namespace test
             data_.last_ptr_ = &data_.first_;
         }
 
-        void erase(const_iterator start, const_iterator end) {
+        void erase(const_iterator i, const_iterator j) {
             node** ptr = &data_.first_;
 
-            while(*ptr != start.ptr_) {
+            while(*ptr != i.ptr_) {
                 ptr = &(*ptr)->next_;
             }
 
-            while(*ptr != end.ptr_) {
+            while(*ptr != j.ptr_) {
                 node* to_delete = *ptr;
                 *ptr = (*ptr)->next_;
                 --data_.size_;