Accept flag parameter in redirect_to_log

Earlier 'redirect_to_log' routine used to direct both 'stdout'
and 'stderr' of a server to its log file. But axfrdns(8) server
requires only 'stderr' to be redirected to its log file. Because
'stdout' is redirected to a network socket by Xinetd(8) or
Systemd(1) service.

Changed 'redirect_to_log' routine to accept a flag parameter.
It'll decide which standard descriptors to redirect to a log file.
It could be an 'OR' of 'STDOUT_FILENO' & 'STDERR_FILENO'.

Changed the server sources to pass this new parameter while calling
'redirect_to_log' routine.
Update axfrdns' xinetd & systemd configurations

axfrdns(8) server depends on Xinetd(8) or Systemd(1) like services
to create a network socket and start the daemon process. axfrdns(8)
need not fork a sub-process to start this daemon.

Changed axfrdns(8) server to avoid creation of a daemon process;
And to only direct its standard error(STDERR_FILENO) descriptor to
a log file. As standard output is directed to a network socket by
its parent process.

Also tweaked the xinetd(8) & Systemd(1) configurations to toggle
the 'wait' parameter and to pass '-D' server argument.

Thank you Edwin Eefting(github.com/psy0rz) for a comprehensive
patch review and for helping to fix the axfrdns(8) server. :)
Retire pickdns server & tools

Retired the 'pickdns' load balancing DNS server and its aide tools;
As they are not installed and are no longer in use.