CQL/CCL/PQF conversion fixes. CCL support for Z39.58 trunc

CQL/CCL/PQF conversion fixes. CCL support for Z39.58 trunc

Lots of fixes for the conversions from CQL to CCL; CCL to RPN;
RPN to CQL. yaz_encode_pqf_term's term parameter properly
escaped into PQF term. CCL truncation configuration t=z
enables Z39.58 truncation which is in fact CCL truncation, but there's
more to it than one might think anyway. The RPN to CCL conversion
handles Z39.58 truncation as well (5=104).