...where index_type has changed from ptrdiff_t to size_t, see <https://
github.com/cplusplus/draft/commit/7f2493e2e2d34b42a6c12c8806e536d4feb3aee3>
"P1227R2 Signed ssize() functions, unsigned size() functions".  Ideally,
ece27693 "Adapt to C++2a std::span<>::index_type
being unsigned size_t" could be simplified now to use std::size_t, but there may
be build environments that include a C++2a <span> that hasn't been adapted to
P1227R2 yet.

Change-Id: I7bfc0da65d415ef06e94d95b5f62030aeb8b35f6
Reviewed-on: https://gerrit.libreoffice.org/69391
Tested-by: Jenkins
Reviewed-by: Stephan Bergmann <sbergman@redhat.com>