new function cxml:doctype

doc/sax.xml

@@ -299,6 +299,7 @@
       <div class="def">Function CXML:ATTRIBUTE* (prefix lname value) => value</div>
       <div class="def">Function CXML:TEXT (data) => data</div>
       <div class="def">Function CXML:CDATA (data) => data</div>
+      <div class="def">Function CXML:doctype (name public-id system-id &amp;optional internal-subset)</div>
       Convenience syntax for event-based serialization.
     </p>
     <p>

xml/package.lisp

@@ -58,6 +58,7 @@
    #:unparse-attribute
    #:cdata
    #:text
+   #:doctype
 
    #:xml-parse-error
    #:well-formedness-violation

xml/unparse.lisp

@@ -564,6 +564,12 @@
 (defmacro with-namespace ((prefix uri) &body body)
   `(invoke-with-namespace (lambda () ,@body) ,prefix ,uri))
 
+(defun doctype (name public-id system-id &optional internal-subset)
+  (sax:start-dtd *sink* name public-id system-id)
+  (when internal-subset
+    (sax:unparsed-internal-subset *sink* internal-subset))
+  (sax:end-dtd *sink*))
+
 (defun maybe-emit-start-tag ()
   (when *current-element*
     ;; starting child node, need to emit opening tag of parent first: