wasm: fix unicode toUpper issues

see https://github.com/kripken/emscripten/issues/4540



On large bitfields, emscripten creates types such as
i472, which 'legalization passes don't know how to
convert into legal code'
Adding a dummy field every 64 bits forces alignment
which in turn forces emscripten to create i64 types
instead.

Task-number: QTBUG-66621
Task-number: QTBUG-69421
Change-Id: I5bfd2079ac8f35ced8b59a1d2e3c657993a70986
Reviewed-by: Eskil Abrahamsen Blomfeldt <eskil.abrahamsen-blomfeldt@qt.io>