This packs the stdio implementation from [1] as alternative to
what the used standard C lib provides with the intent to provide a
thread-safe, smaller, and more feature-complete alternative on
newlib targets.
Compared to `newlib_nano` this reduces `.text` by a bit more than 200 B
while adding support for standard format specifiers such as `RPIu8`,
`PRIu16`, `PRIu64`, `%z`, and `%t`.
Note that `newlib_nano`'s stdio can be thread-safe in reentrant mode
at the cost of RAM (per thread) and latency. Especially the increase
in latency can be prohibitive when real time requirements need to be
met.
[1]: https://github.com/mpaland/printf
