RFA: Support Windows extended error numbers in safe_strerror

[Michael Snyder]

Mark Kettenis wrote:

> GDB is written for POSIX systems.  

Hmmmm, don't know about that.  GDB was written for the Hurd.
Even I don't go back that far, but Fred Fish does -- I see a
Usenet post from Fred saying that he had version 1.1 of gdb
back in January of '87.  (Hey Fred -- any chance you've still
got that?   <g>)

Posix was being whispered about at least as early as '86, but
I don't think GNU was conceived as being Posix-compliant until
way later (if at all).