Sync shared_count.hpp with trunk.

[SVN r51484]

include/boost/detail/shared_count.hpp

@@ -28,6 +28,7 @@
 #include <boost/detail/bad_weak_ptr.hpp>
 #include <boost/detail/sp_counted_base.hpp>
 #include <boost/detail/sp_counted_impl.hpp>
+#include <boost/detail/workaround.hpp>
 // In order to avoid circular dependencies with Boost.TR1
 // we make sure that our include of <memory> doesn't try to
 // pull in the TR1 headers: that's why we use this header 
@@ -227,6 +228,18 @@ public:
         if( pi_ != 0 ) pi_->add_ref_copy();
     }
 
+#if defined( BOOST_HAS_RVALUE_REFS )
+
+    shared_count(shared_count && r): pi_(r.pi_) // nothrow
+#if defined(BOOST_SP_ENABLE_DEBUG_HOOKS)
+        , id_(shared_count_id)
+#endif
+    {
+        r.pi_ = 0;
+    }
+
+#endif
+
     explicit shared_count(weak_count const & r); // throws bad_weak_ptr when r.use_count() == 0
     shared_count( weak_count const & r, sp_nothrow_tag ); // constructs an empty *this when r.use_count() == 0
 
@@ -368,6 +381,11 @@ public:
         return pi_ != 0? pi_->use_count(): 0;
     }
 
+    bool empty() const // nothrow
+    {
+        return pi_ == 0;
+    }
+
     friend inline bool operator==(weak_count const & a, weak_count const & b)
     {
         return a.pi_ == b.pi_;