Luiz Angelo Daros de Luca authored Sep 18, 2017 and Olaf Meeuwissen committed Sep 29, 2017

Flags like -a, -d and -s have many overlap effects. This patch restricts
the effect of flags to a simple action.

New -u (user) flag replaces -a optional argument for running saned as a different user.
The code that retrieve the user info and drop privileges migrated to runas_user().
As a side effect, PID file can be created even if getting user info fails.

New -l (listen) flag sets run_mode to standalone.
New -D (daemonize) flag daemonizes saned after bind.
New -o (once) make saned exit after the first client disconnects.
Flag -s (syslog) is gone. Previous behavior can be reproduced with '-a -d level -o -f'.
New -e (stderr) flag for redirecting output to stderr, instead of syslog.

Flag -d (debug) now only sets the debug level and argument is required. Previous behavior
can be reproduced with '-a -d level -o -f -e'.

The run_mode SANED_RUN_DEBUG and SANED_RUN_ALONE shared most of its code
path. With the new flags dealing with their difference, SANED_RUN_DEBUG is gone.

Flag '-a' still works as before but it can be replaced by '-l -D -u user'.

Current uses of -d (debug) or -s (syslog) will break.

Signed-off-by: Luiz Angelo Daros de Luca <luizluca@gmail.com>