Support for SRU and SRW. Mostly this is provided by the YAZ GFS, but

changes are needed to allow for the case where there is no RPN query
(due to absent on invalid <cql2rpn> element in GFS configuration) so
that CQL is passed through natively; and also to fake up an {REQ_FORM}
and {REP_FORM} parameters set to the "text/xml" OID when this
information is not specified by the GFS.