(see also discussion at <https://gerrit.libreoffice.org/#/c/59204/11> "new
loplugin:conststringfield" about its changes to registry/source/regimpl.cxx)

Change-Id: Id2743adbfeb4d7c42105a65ba8400d7051da2f03
Reviewed-on: https://gerrit.libreoffice.org/59873
Tested-by: Jenkins
Reviewed-by: Stephan Bergmann <sbergman@redhat.com>