Compile errors in json2.hpp and json_structures.hpp

I fixed the following compile errors with g++ 4.7.2:

    jsoncons/src/jsoncons/json2.hpp: In member function ‘jsoncons::basic_json<Char, Storage>::object& jsoncons::basic_json<Char, Storage>::object_value()’:
    jsoncons/src/jsoncons/json2.hpp:1436:10: error: ‘json_object_t’ was not declared in this scope
    jsoncons/src/jsoncons/json_structures.hpp: In copy constructor ‘jsoncons::json_array<Char, Storage>::json_array(const jsoncons::json_array<Char, Storage>&)’:
    jsoncons/src/jsoncons/json_structures.hpp:155:11: error: class ‘jsoncons::json_array<Char, Storage>’ does not have any field named ‘members_’