Unordered: Merge from trunk

- Remove use of BOOST_DEDUCED_TYPENAME and BOOST_UNORDERED_PAIR_CAST, it's
  unlikely that the compilers which require them will be able to cope with the
  new version of unordered.
- Use the old equality algorithm if BOOST_UNORDERED_DEPRECATED_EQUALITY is
  defined.
- Use SFINAE to control which overloads of `construct_impl` are available.
  Fixes problems with differing overload resolution on different compilers.
- Support for piecewise pair construction.
- Only support the old variadic pair construction when
  BOOST_UNORDERED_DEPRECATED_PAIR_CONSTRUCT is defined (also fixed some bugs).
- Avoid instantiating BOOST_RV_REF for non-classes.
- Support optional allocator member functions for compilers with SFINAE
  expressions and Visual C++ 9.0/10.0
- Follow boost macro naming conventions.
- Improved portability for `allocator_traits` emulation.

Current compiler support:

- Full support for GCC 4.4+, Visual C++ 9.0+, Clang.
- All other compilers odn't support optional allocator members.
- No other errors for GCC 3.4.6+, Visual C++ 8.0, Intel, Pathscale.
- Visual Age has a compile error if `select_on_container_copy_construction`
  isn't `const` (it should ignore it).
- `select_on_container_copy_construction` detection doesn't work on Sun.
- `unnecessary_copy_tests` is failling for vacpp on AIX, but not on linux.
- Warnings causing failures for Visual C++ with STLport and WM5.


[SVN r74234]

test/unordered/compile_set.cpp

@@ -16,7 +16,7 @@
 #include "./compile_tests.hpp"
 
 // Explicit instantiation to catch compile-time errors
-/*
+
 template class boost::unordered_set<
     int,
     boost::hash<int>,
@@ -27,7 +27,7 @@ template class boost::unordered_multiset<
     boost::hash<int>,
     std::equal_to<int>,
     test::minimal::allocator<int> >;
-*/
+
 template class boost::unordered_set<
     test::minimal::assignable,
     test::minimal::hash<test::minimal::assignable>,