General:
========
* buildsystem - undo co-installability of Qt5 and Qt6 headers.
  It would require that kdwsdl2cpp generates #include <KDSoapClient-qt6/KDSoapJob.h>
  which in turn would break the build of KDSoap itself, so this gets tricky.

Client-side:
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*

Server-side:
============
*

WSDL parser / code generator changes, applying to both client and server side:
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*