Fixed compilation of filter_iterator conversion constructor.

The constructor would attempt to access a private member of the source
iterator, which could have a different type and therefore have that
member inaccessible. Also, the storage forwarding constructor had incorrect
types used in the forwarding expressions, which caused further compilation
errors.

Fixes #90.

Author: Lastique

include/boost/iterator/filter_iterator.hpp

@@ -46,6 +46,9 @@ class filter_iterator :
 {
     friend class iterator_core_access;
 
+    template< typename, typename >
+    friend class filter_iterator;
+
 private:
     using super_t = detail::filter_iterator_base_t< Predicate, Iterator >;
 
@@ -75,7 +78,7 @@ class filter_iterator :
 
         template< typename Pred, typename Iter >
         storage(Pred&& pred, Iter&& end) :
-            predicate_base(boost::empty_init_t{}, static_cast< Predicate&& >(pred)), m_end(static_cast< Iterator&& >(end))
+            predicate_base(boost::empty_init_t{}, static_cast< Pred&& >(pred)), m_end(static_cast< Iter&& >(end))
         {
         }