nonstd-lite/nonstd-lite#72

* Convert example/16-trompeloeil-runtime.cpp to UTF-8

* Fix some transcoding glitches in CHANGES.txt

This file is UTF-8, but some characters were munged during transcoding
at some point, leading to replacement character U+FFFD (UTF-8 byte
sequence EF BF BD) appearing at several points.

This commit reconstructs the original intended characters.

…hanks @musicinmybrain)

Unconditionally include `cstdio` for `fflush` and friends, and `cstdlib`
for `abort`. When `_WIN32` is not defined, include `unistd.h` instead of
`io.h` for `dup` and `dup2`.

A while ago the 'ubuntu-latest' image moved from Ubuntu 22.04 to
Ubuntu 24.04. See <actions/runner-images#10636>.
However, Ubuntu 24.04 does not have packages for Clang 11 and 12
anymore, thus the Clang jobs fail when they try to install the
corresponding compilers. Therefore, the workflow is changed to
use 'ubuntu-22.04' instead of 'ubuntu-latest'.

Furthermore, a job for Clang 19 (latest Clang version available
on Ubuntu 24.04) is added to run tests with a newer version, too.

…_cpp03.hpp

See log for https://github.com/gsl-lite/gsl-lite/blob/feature/v1.0/test/lest_cpp03.hpp

nonstd-lite/nonstd-lite#73

…#82, thanks @mazunki)

…g. on mingw64 on Ubuntu (#81, thanks @geghamyan variant-lite PR 57)