Description:
------------
I don't know if this is a bug or a "feature" but I noticed that if I set a property with an ampersand or left/right arrow, it creates bad xml when executing saveString.  If this is a "feature", then I suggest that it should be documented in SDO DAS XML with a link to htmlspecialchars.

Reproduce code:
---------------
<?xml version="1.0" encoding="UTF-8"?>
<xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema">

<xsd:element name="request" type="requestType"/>

<xsd:complexType name="requestType" abstract="true"/>

<xsd:complexType name="collectionInfo">
  <xsd:complexContent>
    <xsd:extension base="requestType">
      <xsd:sequence minOccurs="0" maxOccurs="unbounded">
        <xsd:element name="collection">
          <xsd:simpleType>
            <xsd:restriction base="xsd:token">
              <xsd:minLength value="2"/>
              <xsd:maxLength value="2"/>
            </xsd:restriction>
          </xsd:simpleType>
        </xsd:element>
      </xsd:sequence>
      <xsd:attribute name="kind" type="xsd:string"
fixed="collectionInfo"/>
    </xsd:extension>
  </xsd:complexContent>
</xsd:complexType>

<xsd:element name="request-list">
  <xsd:complexType>
     <xsd:sequence>
        <xsd:element ref="request" minOccurs="0"
maxOccurs="unbounded"/>
     </xsd:sequence>
  </xsd:complexType>
</xsd:element>

</xsd:schema>


<?php
header('Content-type: application/xml');
try {
        $xmldas = SDO_DAS_XML::create("request.xsd");
        try {
                $doc = $xmldas->createDocument('', 'request-list');
                $rdo = $doc->getRootDataObject();
                $request = $xmldas->createDataObject('', 'collectionInfo');
                $request->collection->insert('foo < & > bar');
                $request->kind = 'collectionInfo';
                $rdo->request->insert($request);
                print($xmldas->saveString($doc));
        } catch (SDO_Exception $e) {
                print($e);
        }
} catch (SDO_Exception $e) {
        print("Problem creating an XML document: " . $e->getMessage());
}

?>

Expected result:
----------------
<?xml version="1.0" encoding="UTF-8"?>
<request-list xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"><request xsi:type="collectionInfo" kind="collectionInfo"><collection>foo &lt; &amp; &gt; bar</collection></request></request-list>

Actual result:
--------------
<?xml version="1.0" encoding="UTF-8"?>
<request-list xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"><request xsi:type="collectionInfo" kind="collectionInfo"><collection>foo < & > bar</collection></request></request-list>