[PATCH 3/5] signal: Move sys_errlist to a compat symbol

[Florian Weimer]

* Adhemerval Zanella via Libc-alpha:

> +* The deprecated sys_errlist, _sys_errlist, sys_nerr, and _sys_nerr arrays
> +  are non longer available to newly linked binaries, and their declarations
> +  have removed from from <errno.h>.  They are exported solely as
> +  compatibility symbols to support old binaries.  All programs should use
> +  strerror or strerror_r instead.

Should this reference <stdio.h>, and not <errno.h>?

It's again a removal without a formal deprecation warning.  Maybe this
one is more justified given that our error list is currently
incomplete on Linux, and we would have to add a new symbol version to
fix that.