Cleanup header includes.

1. Make inclusion of boost/bind/bind.hpp conditional in some cases, when the
   code actually conditionally uses boost::bind. Reduces compile-time overhead
   and fixes https://github.com/boostorg/thread/issues/307.

2. Remove some unnecessary uses of boost::ref. This allows to avoid including
   boost/core/ref.hpp in a few places, and avoids the associated template
   instantiation overhead in others.

3. Replace deprecated header includes with the more recent alternatives. For
   example: boost/detail/lightweight_test.hpp -> boost/core/lightweight_test.hpp,
   boost/ref.hpp -> boost/core/ref.hpp.

4. Replace some blanket includes with the more fine-grained ones. For example,
   boost/utility.hpp, boost/atomic.hpp. This reduces compile time overhead.

5. Add some missing includes, for example, boost/core/ref.hpp and
   boost/type_traits/is_same.hpp.

6. Replace uses of std::is_same with boost::is_same (with the corresponding
   included header) since the standard type_traits header presence and validity
   is not tested by the code. Using boost::is_same makes the code more portable.

test/test_3837.cpp

@@ -7,7 +7,8 @@
 #include <boost/thread.hpp>
 #include <boost/thread/thread_only.hpp>
 #include <boost/optional.hpp>
-#include <boost/detail/lightweight_test.hpp>
+#include <boost/bind/bind.hpp>
+#include <boost/core/lightweight_test.hpp>
 
 using namespace boost;
 using namespace boost::chrono;