Error in source code, after down grade cross compiler from gcc4.9.2 to gcc4.4.1

I am currently working on arm-unknown-linux-gnueabi and downgraded compiler from gcc4.9.2 to gcc4.4.1. I used crosstool-ng to compile compiler with gcc4.4.1.As you know gcc4.9.2 supports more c++11 features then gcc4.4.1. Code was compiling with no errors with 4.9.2 but faces errors with 4.4.1. Following is the error which i can't understand why ? Code is,

class dl_loader {
    // Dl loader
    dl_loader( dl_loader& ) = delete;
    dl_loader& operator=( dl_loader& ) = delete;
    dl_loader() {
    }
public:
    ~dl_loader() {
        if (_instance_) {
            delete _instance_; _instance_ = NULL;
        }
    }
public:
    static dl_loader * get_instance();
    //Resolve name by svc_net.so.1:name
    template <typename Func, typename ...Args>
    typename std::function<Func>::result_type call( const char* name, Args && ...args ) 
    {
        Func* fptr = reinterpret_cast<Func*>( find_or_load_symbol( name ) );
        assert(fptr);
        return fptr( args ... );
    }
    template <typename Func>
    typename std::function<Func>::result_type call( const char* name ) 
    {
        Func* fptr = reinterpret_cast<Func*>( find_or_load_symbol( name ) );
        assert(fptr);
        return fptr( );
    }
private:
    //! Find or load symbol from the dynamic library
    void* find_or_load_symbol( const char *name );
private:
    std::map<std::string, void*> m_funcs;   //Function loaded names
**//    using lib_ptr_t = std::unique_ptr<void,std::function<void(void*)>>;  IQ:b/c gcc4.4.1 doesn't support aliases keyword "using"
    typedef std::unique_ptr<void ,std::function<void(void* )>>  lib_ptr_t;**
    std::map<std::string, lib_ptr_t> m_libs;    //Libs loaded
    static dl_loader * _instance_;
};

/! Find or load symbol from the dynamic library
void* dl_loader::find_or_load_symbol( const char *name )
{
    const auto f_it = m_funcs.find( name );
    if( f_it == m_funcs.end() ) 
    {
        const auto sep = std::strstr( name, ":" );
        if( !sep ) 
        {
            throw std::logic_error("Invalid syntax token : not found");
        }
        const auto name_len = sep - name;
        char library_name[ name_len + sizeof('\0') ];
        std::memcpy( library_name, name, name_len ); 
        library_name[name_len] = '\0';
        const auto symbol_name = sep + 1;
        const auto l_it = m_libs.find( library_name );
        void* lib_hwnd {};
        if( l_it == m_libs.end() )
        {
            const auto handle = dlopen( library_name, RTLD_LAZY );
            if( !handle ) 
            {
                throw std::logic_error( std::string("Unable to find library: ") + 
                        library_name );
            }

//          m_libs[ library_name ] = lib_ptr_t ( handle, [](void*d){ dlclose(d); } );


            lib_hwnd = handle;
        } 
        else 
        {
            lib_hwnd = l_it->second.get();
        }
        //Try to open function name from library
        const auto fn_ptr = dlsym( lib_hwnd, symbol_name );
        if( fn_ptr ) 
        {
            m_funcs[ name ] = fn_ptr;
            return fn_ptr;
        } 
        else 
        {
            throw  std::logic_error( std::string("Unable to find symbol: ") +
                symbol_name + " in library: " +  library_name );
        }
    } 
    else 
    {
        return f_it->second;
    }
    return NULL;
}

Thanks in Advance

Errors are

find_or_load_symbol(const char*)':
dynlib_loader.cpp:67: error: expected primary-expression before '(' token
dynlib_loader.cpp:68: error: expected primary-expression before '[' token
dynlib_loader.cpp:68: error: expected primary-expression before ']' token
dynlib_loader.cpp:68: error: expected primary-expression before 'void'
dynlib_loader.cpp:69: error: expected ')' before '{' token
dynlib_loader.cpp:69: error: expected ';' before ')' token