[boost] [Fusion] Patch: fixing some test failures on clang

The following tests of Boost.Fusion fail on clang trunk in a C++11 mode with libc++. * io.test * deque_construction.test * deque_misc.test * std_tuple_iterator.test * invoke.test Attached a patch for fixing two failures (io.test and std_tuple_iterator.test) of them. Regards, Michel