...by introducing OStringBuffer::getMutableStr and (for consistency) OUStringBuffer::getMutableStr Change-Id: I4dfc3b8d8ffb49b8b3742600081d075536b312e5 Reviewed-on: https://gerrit.libreoffice.org/c/core/+/197605 Reviewed-by: Stephan Bergmann <stephan.bergmann@collabora.com> Tested-by: Jenkins