...so that at least Clang -fsanitize=implicit-signed-integer-truncation would
generate warnings for them

Change-Id: I76fd0aaa8e61784053e2b367b302fdd68c3859b4
Reviewed-on: https://gerrit.libreoffice.org/68815
Tested-by: Jenkins
Reviewed-by: Stephan Bergmann <sbergman@redhat.com>