Fix: boost enable directory_iterator C++11 range-base for statement

include/nana/filesystem/filesystem.hpp

@@ -55,6 +55,37 @@
 #define NANA_USING_BOOST_FILESYSTEM 1
 #   include <chrono>
 #   include <boost/filesystem.hpp>
+// dont include generic_u8string
+// http://www.boost.org/doc/libs/1_66_0/boost/filesystem/path.hpp
+// enable directory_iterator C++11 range-base for 
+// http://www.boost.org/doc/libs/1_66_0/boost/filesystem/operations.hpp
+// but travis come with an oooold version of boost
+// NOT enable directory_iterator C++11 range-base for
+// http://www.boost.org/doc/libs/1_54_0/boost/filesystem/operations.hpp
+namespace boost
+{
+	namespace filesystem
+	{
+
+		//  enable directory_iterator C++11 range-base for statement use  --------------------//
+
+		//  begin() and end() are only used by a range-based for statement in the context of
+		//  auto - thus the top-level const is stripped - so returning const is harmless and
+		//  emphasizes begin() is just a pass through.
+		inline
+		const directory_iterator& begin(const directory_iterator& iter) BOOST_NOEXCEPT
+		{
+			return iter;
+		}
+		inline
+		directory_iterator end(const directory_iterator&) BOOST_NOEXCEPT
+		{
+			return directory_iterator();
+		}
+
+	}  // namespace filesystem
+}   
+
 
 // add boost::filesystem into std::experimental::filesystem
 namespace std {
@@ -76,15 +107,15 @@ namespace std {
 				unknown = boost::filesystem::file_type::type_unknown,
 			};
 			/// enable directory_iterator range-based for statements
-			inline directory_iterator begin(directory_iterator iter) noexcept
+			//inline directory_iterator begin(directory_iterator iter) noexcept
-			{
+			//{
-				return iter;
+			//	return iter;
-			}
+			//}
 
-			inline directory_iterator end(const directory_iterator&) noexcept
+			//inline directory_iterator end(const directory_iterator&) noexcept
-			{
+			//{
-				return {};
+			//	return {};
-			}
+			//}
 		} // filesystem
 	} // experimental
 } // std