Previous gai_strerror() returned numeric representation of the code,
but used TLS storage, which might cause issues with stack sizes on all
tasks in the system. Alternatively we can leave the storage to static
only (which wouldn't be thread-safe) or we could one-time allocate and
never free (which is wrong).
This option uses hardcoded strings for common error codes used in lwip.
The disadvantage is that we might need to update the impl in the future
when lwip adds more codes.
Adding a reverse dependency to lwip and define macros, which
enable declarations of socketpair() and gai_strerror() in standard
heders (sys/socket.h and netdb.h)
