daemonization, io socket and file redirection
fix spelling

https://github.com/RIOT-OS/RIOT/pull/405#discussion_r8176584
tcp/unix -> TCP/UNIX
remove superflous variables
don't use warnx with socket io

addresses:
https://github.com/RIOT-OS/RIOT/pull/405#issuecomment-30059387
https://github.com/RIOT-OS/RIOT/pull/405#issuecomment-30065722
add -E option
implement err.h

valgrind reported invalid reads/writes with glibc err[x]|warn[x] (in
glibc printf) when stdio had been redirected in between.

define _progname (pointing to argv[0])
Revert "don't use warnx with socket io"

This reverts commit 3c2f8ba57a032d930358a48d59675066a03a85ef.