xmlGetLineNo() returns invalid value in certain occations when line number equals or is higher than 65535: When node contains only text, line number points to its end tag. When node has children, line number point to a first child node's starting tag.

In other words, line number points to a node's starting tag when a line number is below 65535 and to a next occuring tag when line number is 65535 or higher.

Reproducer:
------------
<?php
if (!defined('LIBXML_VERSION') || LIBXML_VERSION < 20900) die('This test is for libxml >= 2.9.0');

define('LIBXML_BIGLINES', 1<<22);
$foos = str_repeat('<foo/>' . PHP_EOL, 65526);

$xml = <<<EOD
<?xml version="1.0" encoding="UTF-8"?>
<root>
$foos
<bar1>
 <yyy1>123</yyy1>
 <yyy2>123
 </yyy2>
</bar1>
<bar2>
 <zzz1>123</zzz1>
 <zzz2>123
 </zzz2>
</bar2>
</root>
EOD;

$dom = new DOMDocument();
$dom->loadXML($xml, LIBXML_BIGLINES);
echo 'bar1: ' . $dom->getElementsByTagName('bar1')->item(0)->getLineNo() ."<br/>\n";
echo 'yyy1: ' . $dom->getElementsByTagName('yyy1')->item(0)->getLineNo() ."<br/>\n";
echo 'yyy2: ' . $dom->getElementsByTagName('yyy2')->item(0)->getLineNo() ."<br/>\n";
echo 'bar2: ' . $dom->getElementsByTagName('bar2')->item(0)->getLineNo() ."<br/>\n";
echo 'zzz1: ' . $dom->getElementsByTagName('zzz1')->item(0)->getLineNo() ."<br/>\n";
echo 'zzz2: ' . $dom->getElementsByTagName('zzz2')->item(0)->getLineNo() ."<br/>\n";
?>

Expected result:
----------------
bar1: 65530
yyy1: 65531
yyy2: 65532
bar2: 65535
zzz1: 65536
zzz2: 65537

Actual result:
--------------
bar1: 65530 // OK
yyy1: 65531 // OK
yyy2: 65532 // OK
bar2: 65536 // Error
zzz1: 65536 // OK
zzz2: 65538 // Error