-Added support for Z39.50 character set negotiation. This allows
-the proxy to act as a Z39.50 server supporting character set negotiation
-for backends not supporting it. New config element target-charset
-specifies encoding for target, and MUST be specified in order
-for any conversion to take place. Conversion also takes place for
-SRW/SRU clients that are negotiate implicitly to UTF-8.