="identifier">string</span></code> are not defined
            in the namespace <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">spirit</span></code>
            anymore as they have been moved to the character set namespaces, allowing
            to do proper character set handling based on the used namespace (as
            <code class="computeroutput"><span class="identifier">spirit</span><span class="special">::</span><span class="