Use DOM's node creation algorithms in the XML parser

The XML parser only said how to create elements, through create an
element for a token, which always uses a null prefix. The other nodes it
creates had no specified realm, and its processing instructions no
attribute map, so getAttribute() returned null for them.

Give create an element for a token an optional prefix and name a
creation algorithm for each type of node, as
85f453b did for the HTML parser.

Author: annevk

source

@@ -3255,6 +3255,7 @@ a.setAttribute('href', 'https://example.com/'); // change the content attribute
 
     <ul class="brief">
      <li><dfn data-x-href="https://dom.spec.whatwg.org/#interface-attr"><code>Attr</code></dfn> interface</li>
+     <li><dfn data-x-href="https://dom.spec.whatwg.org/#interface-cdatasection"><code>CDATASection</code></dfn> interface</li>
      <li><dfn data-x-href="https://dom.spec.whatwg.org/#interface-characterdata"><code>CharacterData</code></dfn> interface</li>
      <li><dfn data-x-href="https://dom.spec.whatwg.org/#interface-comment"><code>Comment</code></dfn> interface</li>
      <li><dfn data-x-href="https://dom.spec.whatwg.org/#interface-domimplementation"><code>DOMImplementation</code></dfn> interface</li>
@@ -3424,6 +3425,7 @@ a.setAttribute('href', 'https://example.com/'); // change the content attribute
      <li>The <dfn data-x="create an element" data-x-href="https://dom.spec.whatwg.org/#concept-create-element">create an element</dfn> algorithm</li>
      <li>The <dfn data-x-href="https://dom.spec.whatwg.org/#create-a-document">create a document</dfn>,
                  <dfn data-x-href="https://dom.spec.whatwg.org/#create-a-text-node">create a text node</dfn>,
+                 <dfn data-x-href="https://dom.spec.whatwg.org/#create-a-cdata-section-node">create a CDATA section node</dfn>,
                  <dfn data-x-href="https://dom.spec.whatwg.org/#create-a-doctype">create a doctype</dfn>,
                  <dfn data-x-href="https://dom.spec.whatwg.org/#create-a-comment-node">create a comment node</dfn>,
                  <dfn data-x-href="https://dom.spec.whatwg.org/#create-a-processing-instruction-node">create a processing instruction node</dfn>, and
@@ -145001,8 +145003,8 @@ dictionary <dfn dictionary>StorageEventInit</dfn> : <span>EventInit</span> {
 
   <div algorithm>
   <p>To <dfn data-x="create an element for the token">create an element for a token</dfn>, given a
-  token <var>token</var>, a string <var>namespace</var>, and a <code>Node</code> object
-  <var>intendedParent</var>:</p>
+  token <var>token</var>, a string <var>namespace</var>, a <code>Node</code> object
+  <var>intendedParent</var>, and an optional string-or-null <var>prefix</var> (default null):</p>
 
   <ol>
    <li><p>If the <span>active speculative HTML parser</span> is not null, then return the result of
@@ -145054,8 +145056,8 @@ dictionary <dfn dictionary>StorageEventInit</dfn> : <span>EventInit</span> {
 
    <li>
     <p>Let <var>element</var> be the result of <span data-x="create an element">creating an
-    element</span> given <var>document</var>, <var>localName</var>, <var>namespace</var>, null,
-    <var>is</var>, <var>willExecuteScript</var>, and <var>registry</var>.</p>
+    element</span> given <var>document</var>, <var>localName</var>, <var>namespace</var>,
+    <var>prefix</var>, <var>is</var>, <var>willExecuteScript</var>, and <var>registry</var>.</p>
 
     <p class="note">This will cause <span data-x="custom element constructor">custom element
     constructors</span> to run, if <var>willExecuteScript</var> is true. However, since we
@@ -150620,11 +150622,26 @@ console.assert(container.firstChild instanceof SuperP);
 
   <p>This <code>Document</code> must then be populated with DOM nodes that represent the tree
   structure of the input passed to the parser, as defined by <cite>XML</cite>, <cite>Namespaces
-  in XML</cite>, and <cite>DOM</cite>. When creating DOM nodes representing elements,
-  the <span data-x="create an element for the token">create an element for a token</span> algorithm
-  or some equivalent that operates on appropriate XML data structures must be used, to ensure the
-  proper <span data-x="element interface">element interfaces</span> are created and that <span
-  data-x="custom element">custom elements</span> are set up correctly.</p>
+  in XML</cite>, and <cite>DOM</cite>. These nodes must be created using the following
+  algorithms:</p>
+
+  <ul>
+   <li><p>For elements, <span data-x="create an element for the token">create an element for a
+   token</span>, given the element's prefix, to ensure the proper <span data-x="element
+   interface">element interfaces</span> are created and that <span data-x="custom element">custom
+   elements</span> are set up correctly.</p></li>
+
+   <li><p>For <code>Text</code> nodes, <span>create a text node</span>.</p></li>
+
+   <li><p>For <code>CDATASection</code> nodes, <span>create a CDATA section node</span>.</p></li>
+
+   <li><p>For <code>Comment</code> nodes, <span>create a comment node</span>.</p></li>
+
+   <li><p>For <code>ProcessingInstruction</code> nodes, <span>create a processing instruction
+   node</span>.</p></li>
+
+   <li><p>For <code>DocumentType</code> nodes, <span>create a doctype</span>.</p></li>
+  </ul>
 
   <p>For the operations that the <span>XML parser</span> performs on the <code>Document</code>'s
   tree, the user agent must act as if elements and attributes were individually appended and set