lib: posix: support for perror()

[cfriedt]

Is your enhancement proposal related to a problem? Please describe.
The perror() function is helpful shorthand for printing an error message in POSIX applications.

It's fairly trivial to implement when relying on strerror() and consumes very little space.

OTOH, it's a major annoyance to #ifdef-out perror in 3rd-party libraries.

Describe the solution you'd like

A perror() implementaiton.

Describe alternatives you've considered
#ifdef-ing out code ad-infinitum

Additional context