axutil_qname_to_string serialize with the prefix.

Currently the axutil_qname_to_serialize function serialize the qname with the prefix.
"localpart|namespace_uri|prefix"

This cause problems in comparing qnames,

I.e. although axutil_qname_equals has get rid of this using different approaches (just not comparing prefixes), In other places like axiom this serialized strings kept in the hashes. (e.g. attribute hash in the element).
This leads axiom_element_get_attribute not to work on occasions where the prefix of the given qname is different. This is a problem for interoperability.

I think these bugs can be fixed if we remove the prefix in the serialized string generated from axutil_qname_to_string