More -Wunused-local-typedef warnings when building Boost 1.54.0 with gcc 4.8.1

[lcarreon@…]

These are the unused-local-typedef warnings specific to Boost.Xpressive:

./boost/xpressive/regex_algorithms.hpp:306:57: warning: typedef ‘char_type’ locally defined but not used [-Wunused-local-typedefs]

typedef typename iterator_value<BidiIter>::type char_type;

./boost/xpressive/detail/dynamic/parser.hpp:331:53: warning: typedef ‘char_type’ locally defined but not used [-Wunused-local-typedefs]

typedef typename iterator_value<BidiIter>::type char_type;