Description:
------------
libxml defines a constant LIBXML_NOXMLDECL, however DOMDocument doesn't currently honor this variable. It is an extremely useful/important feature because XHTML with an XML declaration triggers "quirks" mode in IE6. 

Similarly, XSLTProcessor does not honor the "omit-xml-declaration" attribute of the <xsl:output> element. 

It would be very useful if support for one or both of these items were added. 


Reproduce code:
---------------
---
From manual page: libxml.constants
---

<?php

print "PHP_VERSION:      ".PHP_VERSION."\n";
print "LIBXML_VERSION:   ".LIBXML_VERSION."\n";
print "LIBXML_NOXMLDECL: ".LIBXML_NOXMLDECL."\n";

$dom = new DomDocument();
$dom->loadXML("<foo />");

# This should work but doesn't.

print "DOMDocument doesn't honor LIBXML_NOXMLDECL:\n";
print $dom->saveXML(null,LIBXML_NOXMLDECL);

# This works, and will still work after the above is fixed.

print "Forwards compatible workaround:\n";
$lines = explode("\n", $dom->saveXML(null, LIBXML_NOXMLDECL), 2);
if(!preg_match('/^\<\?xml/', $lines[0]))
    print $lines[0];
print $lines[1];

?>


Expected result:
----------------
PHP_VERSION:      5.3.0
LIBXML_VERSION:   20703
LIBXML_NOXMLDECL: 2
DOMDocument doesn't honor LIBXML_NOXMLDECL:
<foo/>
Forwards compatible workaround:
<foo/>


Actual result:
--------------
PHP_VERSION:      5.3.0
LIBXML_VERSION:   20703
LIBXML_NOXMLDECL: 2
DOMDocument doesn't honor LIBXML_NOXMLDECL:
<?xml version="1.0"?>
<foo/>
Forwards compatible workaround:
<foo/>