reattach to the syslog-ng console from syslog-ng-ctl

[bazsi]

This PR allows syslog-ng-ctl to connect back to syslog-ng's original stdin/out/err fds and re-acqiure the output on those fds.

There are three subcommands:

# this just takes the stdio fds for 10 seconds and displays syslog-ng output in that time period
$ syslog-ng-ctl attach stdio --seconds 10

The other allows you to steal the log messages:

$ syslog-ng-ctl attach logs --seconds 10 --level trace

The other allows you to start the debugger on the new console:

$ syslog-ng-ctl attach debugger

There can only be one such attached process at any time.