Description:
------------
A specific error in the XML Schema (XSD) causes the DomDocument validator to crash. The error occurs in the php5ts.dll.

Reproduce code:
---------------
<?php

$schema = <<<XSD
<?xml version="1.0" encoding="utf-8" ?>
<xs:schema attributeFormDefault="unqualified" elementFormDefault="qualified" xmlns:xs="http://www.w3.org/2001/XMLSchema">
  <xs:element default="NEM" name="root">
    <xs:simpleType>
      <xs:restriction base="_valaszto">
					<xs:enumeration value="IGEN" />
					<xs:enumeration value="NEM" />
					<xs:whiteSpace value="preserve" />
	  </xs:restriction>
    </xs:simpleType>
  </xs:element>
  <xs:simpleType name="_valaszto">
    <xs:restriction base="xs:string">
      <xs:enumeration value="IGEN" />
      <xs:enumeration value="NEM" />
      <xs:whiteSpace value="collapse" />
    </xs:restriction>
  </xs:simpleType>
</xs:schema>
XSD;

$xml = <<<XML
<root>
</root>
XML;

$dom = new DomDocument();
$dom->loadXML( $xml );
$dom->schemaValidateSource( $schema );

?>

Expected result:
----------------
Warning: DOMDocument::schemaValidateSource() [domdocument.schemavalidatesource]: Invalid Schema in C:\wwwroot\ingatlanok2_trunk\validator.php on line 32

Actual result:
--------------
The httpd.exe crashes.