Cannot build gnash with clang-3.8.0:

In file included from gnash.cpp:52:
../libbase/accumulator.h:103:16: error: allocating an object of abstract class type 'accumulator_type<int>'
    return new accumulator_type<T>();
               ^
gnash.cpp:285:19: note: in instantiation of function template specialization 'accumulator<int>' requested here
    ("verbose,v", accumulator<int>()
                  ^
/usr/include/boost/program_options/value_semantic.hpp:44:22: note: unimplemented pure virtual method
      'adjacent_tokens_only' in 'accumulator_type'
        virtual bool adjacent_tokens_only() const = 0;
                     ^
1 error generated.