[xml] xpath contains() function

["Vakoc, Mark" <Mark_Vakoc jdedwards com>]

I seem to get differing results from various processers when using the xpath
contains() function with the second string as an empty string.  I checked
the spec( http://www.w3.org/tr/xpath#function-contains and it makes no
mention of this case.

Other processors tested evaluate contains('test','') to false, while libxml
returns true which doesn't seem correct to me.  Any idea on who is correct?