...to avoid -Werror,-Wshadow from Clang trunk with
<https://reviews.llvm.org/D52400> "Improve -Wshadow warnings with enumerators",
warning about shadowing of userSpaceOnUse in enum SvgUnits in
svgio/inc/svgtools.hxx

Change-Id: Ie1438e6ad0f73c73ad643157e5f8366a6e3f6851
Reviewed-on: https://gerrit.libreoffice.org/61933
Tested-by: Jenkins
Reviewed-by: Stephan Bergmann <sbergman@redhat.com>