To save binary size, currently just returns textual name of error
code, e.g. EAI_FAIL -> "EAI_FAIL". Based on real usecases, can be
replaced with user-friendly message later. (Current usecase is to
allow/help to elaborate sockets API by proof-of-concept porting
existing socket apps).
Signed-off-by: Paul Sokolovsky <paul.sokolovsky@linaro.org>