Permit escaped SSML docs in addition to CDATA

Fixes #70

extensions/xep-0327.xml

@@ -1273,7 +1273,7 @@
     ]]></example>
 
     <section3 topic='Output Component' anchor='session-component-execution-output'>
-      <p>Media output is a core concept in Rayo, and is provided by the output component. The component allows media to be rendered to a call or a mixer, using the server's local media server. A server MUST support audio file playback and MUST support the text/uri-list document format. A server MAY support speech synthesis and MAY support <link url='http://www.w3.org/TR/speech-synthesis/'>SSML</link>. The component is created using an <link url='def-component-output'>&lt;output/&gt; command</link>, containing one or more documents to render, along with a set of options to determine the nature of the rendering.</p>
+      <p>Media output is a core concept in Rayo, and is provided by the output component. The component allows media to be rendered to a call or a mixer, using the server's local media server. A server MUST support audio file playback and MUST support the text/uri-list document format. A server MAY support speech synthesis and MAY support <link url='http://www.w3.org/TR/speech-synthesis/'>SSML</link> (in which case the document should be escaped or enclosed in CDATA). The component is created using an <link url='def-component-output'>&lt;output/&gt; command</link>, containing one or more documents to render, along with a set of options to determine the nature of the rendering.</p>
 
       <example caption='Client renders a simple SSML document to a call'><![CDATA[
 <iq from='juliet@capulet.lit/balcony'