Description:
------------
When NS-aware parser is created, the handler set by xml_set_start_namespace_decl_handler() is never called for default namespace given in the DOCTYPE attribute, when the root tag is processed.

See also https://bugs.php.net/bug.php?id=71593

Test script:
---------------
<?php
$indent = '';
$parser = xml_parser_create_ns('UTF-8');

xml_set_start_namespace_decl_handler($parser, function($self, $name, $target)
  {
    global $indent;
    $ns = $name ?: '(default)';
    print $indent . "NS:{$ns} {$target}\n";
  });

// Expecting the notion of NS:(default) when the root tag is processed.
xml_parse($parser, '<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE shape PUBLIC "-//Dia//DTD Dia shape 1.0//EN" "http://www.daa.com.au/~james/dia-shape-ns">
<shape xmlns:svg="http://www.w3.org/2000/svg">
  <name>Custom - Styles mix</name>
</shape>', true);

print xml_error_string(xml_get_error_code($parser)) . "\n";
?>

Expected result:
----------------
NS:(default) http://www.daa.com.au/~james/dia-shape-ns
NS:svg http://www.w3.org/2000/svg
No error

I.e. NS(default) should be printed when root tag is processed (before root element handler is called).

Actual result:
--------------
NS:svg http://www.w3.org/2000/svg
No error