...to avoid -Werror,-Wshadow from Clang trunk with
<https://reviews.llvm.org/D52400> "Improve -Wshadow warnings with enumerators",
warning about shadowing of UNKNOWN in e.g. enum ESCHER_BlibType in
include/filter/msfilter/escherex.hxx

Change-Id: Id6608474e76730be4c439f480c31f661b8b5748e
Reviewed-on: https://gerrit.libreoffice.org/62013
Tested-by: Jenkins
Reviewed-by: Stephan Bergmann <sbergman@redhat.com>