Fix transparent erase signature to "K&&"

Author: igaztanaga

include/boost/container/detail/flat_tree.hpp

@@ -1175,8 +1175,9 @@ class flat_tree
       !dtl::is_convertible<K, iterator>::value &&     //not convertible to iterator
       !dtl::is_convertible<K, const_iterator>::value  //not convertible to const_iterator
       , size_type>::type
-      erase(const K& k)
+      erase(BOOST_FWD_REF(K) key)
    {
+      const typename remove_cvref<K>::type & k = key;  //Support emulated rvalue references
       std::pair<iterator, iterator > itp = this->equal_range(k);
       size_type ret = static_cast<size_type>(itp.second - itp.first);
       if (ret) {

include/boost/container/detail/tree.hpp

@@ -1152,8 +1152,11 @@ class tree
       !dtl::is_convertible<K, iterator>::value &&     //not convertible to iterator
       !dtl::is_convertible<K, const_iterator>::value  //not convertible to const_iterator
       , size_type>::type
-      erase(const K& k)
-   {  return AllocHolder::erase_key(k, KeyNodeCompare(key_comp()), alloc_version()); }
+      erase(BOOST_FWD_REF(K) key)
+   {
+      const typename remove_cvref<K>::type & k = key;  //Support emulated rvalue references
+      return AllocHolder::erase_key(k, KeyNodeCompare(key_comp()), alloc_version());
+   }
 
    template <class K>
    inline typename dtl::enable_if_c<

include/boost/container/flat_map.hpp

@@ -1333,7 +1333,7 @@ class flat_map
       !dtl::is_convertible<K BOOST_MOVE_I iterator>::value &&     //not convertible to iterator
       !dtl::is_convertible<K BOOST_MOVE_I const_iterator>::value  //not convertible to const_iterator
       BOOST_MOVE_I size_type>::type)
-      erase(const K& x)
+      erase(BOOST_FWD_REF(K) x)
    {  return m_flat_tree.erase_unique(x); }
 
    //! <b>Effects</b>: Erases all the elements in the range [first, last).

include/boost/container/map.hpp

@@ -1032,7 +1032,7 @@ class map
             !dtl::is_convertible<K BOOST_MOVE_I iterator>::value &&     //not convertible to iterator
             !dtl::is_convertible<K BOOST_MOVE_I const_iterator>::value  //not convertible to const_iterator
             BOOST_MOVE_I size_type>::type)
-      erase(const K& x)
+      erase(BOOST_FWD_REF(K) x)
       { return this->base_t::erase_unique(x); }
 
    #if defined(BOOST_CONTAINER_DOXYGEN_INVOKED)