merging attributes (with xsl:copy?)

I'm looking for a way to match all elements <x> (which may have
attributes) and add new attributes:
    
    <x>                 --> <x             b="b" c="c">
    <x a="a">           --> <x a="a"       b="b" c="c">
    <x a="a" d="d">     --> <x a="a" d="d" b="b" c="c">

When <x> has no attributes this is easy: 

    <xsl:template match="x">
        <x b="b" c="c">
            <xsl:apply-templates/>
        </x>
    </xsl:template>

But how to copy all existing attributes to the new element?  I'm sorry
in case this is a FAQ - I did not found it in the XSL archive. 

-- Christian
 
-- 
 Christian Lindig       Gaertner Datensysteme GbR, Braunschweig, Germany 
                        lindig@xxxxxxxxxxx http://www.gaertner.de/~lindig 


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