Add a level of inheritance above SocketHandler

SocketHandler has been renamed to TCPSocketHandler
SocketHandler is now a simple interface with a few methods, used only by
Poller.

This way we can inherite from the new SocketHandler class, to handle other
types of sockets, and still make them manageable by the poller without any
change in the Poller class.

Also remove that from the spec file

Remove biboumi_logdir from the spec file

Run the test_suite in the spec %check section

Fix a typo

Enable assert() even in release mode, in the test_suite

Provide a spec file to build a Fedora RPM

Use systemd-daemon logging prefix if available

Provide an example unit file for systemd

Provide an example configuration file

Regularly send a notification for the systemd watchdog

Fix some cmake issues

fix #2551

Add missing <string> include in timed_events.hpp

fix #2552

Fix ad-hoc “disconnect user” command. Do not add the <error/> on success

Add some details in the INSTALL file

Provide a make dist target

Little documentation update

Rename cmake target test->test_suite for cmake 3.0

See CMP0037

Delete the timeout event using the correct socket number, instead of -1

Was causing the event to not be removed in case of connection failure, which
lead to a dangling timed event named “timeout-1”, which was called later, by
some other SocketHandler for which even the socket creation failed (so, its
socket is -1), with a pointer to the previous SocketHandler which has
disappeared for a long time: segmentation fault etc.

Support version request to IRC users