+--- 2.1.20 2006/06/02
+
+Bug #600: SRU GET, POST support for yaz-client. Introduced
+command 'sru' which selects method SOAP/GET/POST.
+
Allow missingValueAction to be specified for the sortspec string -
function yaz_sort_spec. By default, the missing value action is null.
Use ! to specify "abort". Use = followed by stringvalue to specify default