Carriage returns in attribute values (poss libxslt bug)?

Hi --

Are there any special rules around XSLT processing of string values from 
attributes vs text() nodes? I've noticed the libxslt seems to strip out 
carriage returns. CRs are probably pretty rare in attribute values, but 
MSXML seems to handle them ok so I'm wondering if there any special 
rules I don't know about. I took a quick look through the XSLT spec and 
didn't seen anything.
Here's how to reproduce it. Given this XML:

<?xml version="1.0" encoding="UTF-8"?>
<?xml-stylesheet type="text/xsl" href="U:\Active 
Workspace\Development\IKRS\CentralClassifier\libxslt-bug.xslt"?>
<libxml>
        <foo a="alpha
beta
delta"/>
</libxml>

and this stylesheet:

<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform";>
        <xsl:output method="xml" version="1.0" encoding="UTF-8" indent="yes"/>
        <xsl:template match="foo">
        <attribute><xsl:value-of select="@a"></xsl:value-of></attribute>
        </xsl:template>
</xsl:stylesheet>

MSXML produces:

<?xml version="1.0" encoding="UTF-8"?>
<attribute>alpha
beta
delta</attribute>

whereas libxslt produces:

<?xml version="1.0" encoding="UTF-8"?>

       <attribute>alpha beta delta</attribute>

Any ideas?

Thanks!

Ramon