Changes for 1.56 made during Git transition:

*  Improved Doxygen generated reference and updated and fixed forward-declaration header.

*  Source breaking: Removed previously deprecated `xxx_dont_splay` functions from splay containers and removed `splay_set_base_hook` and `splay_set_member_hook`from splay containers.

include/boost/intrusive/pointer_plus_bits.hpp

@@ -13,6 +13,8 @@
 #ifndef BOOST_INTRUSIVE_POINTER_PLUS_BITS_HPP
 #define BOOST_INTRUSIVE_POINTER_PLUS_BITS_HPP
 
+#include <boost/intrusive/detail/config_begin.hpp>
+#include <boost/intrusive/intrusive_fwd.hpp>
 #include <boost/intrusive/detail/mpl.hpp> //ls_zeros
 #include <boost/intrusive/detail/assert.hpp> //BOOST_INTRUSIVE_INVARIANT_ASSERT
 
@@ -83,4 +85,6 @@ struct pointer_plus_bits<T*, NumBits>
 } //namespace intrusive
 } //namespace boost
 
+#include <boost/intrusive/detail/config_end.hpp>
+
 #endif //BOOST_INTRUSIVE_POINTER_PLUS_BITS_HPP