Issue #2746: Don't escape ampersands and angle brackets ("&", "<", ">")
in XML processing instructions and comments.  These raw characters are
allowed by the XML specification, and are necessary when outputting e.g.
PHP code in a processing instruction.  Patch by Neil Muller.
diff --git a/Lib/xml/etree/ElementTree.py b/Lib/xml/etree/ElementTree.py
index 7dbc72e..e5afcbc 100644
--- a/Lib/xml/etree/ElementTree.py
+++ b/Lib/xml/etree/ElementTree.py
@@ -666,9 +666,9 @@
         # write XML to file
         tag = node.tag
         if tag is Comment:
-            file.write("<!-- %s -->" % _escape_cdata(node.text, encoding))
+            file.write("<!-- %s -->" % _encode(node.text, encoding))
         elif tag is ProcessingInstruction:
-            file.write("<?%s?>" % _escape_cdata(node.text, encoding))
+            file.write("<?%s?>" % _encode(node.text, encoding))
         else:
             items = node.items()
             xmlns_items = [] # new namespaces in this scope