Update libvirt to 2.1

Update libvirt to 2.1

This is the update of libvirt to the latest version 2.1.
The most important change from a packager view is the new virtlogd
daemon.
This daemon handles the qemu output and wrote it to log files.

The require some changes:
- A new init script to start, stop restart the daemon called virtlogd.
The daemon is restart with SIGUSR1 (this is important because the daemon
keeps all pipelines etc. open).

This introduces a problem with the uninstall.sh install.sh script.
It is not possible to stop the daemon while virtual machines are
running, so the script update.sh execute from now not uninstall.sh and
install.sh instead it contains all steps from uninstall.sh install.sh
expect the start / stop routine for virtlogd. The daemon is just
restarted after the update, which makes sure that all changes take
effect.

- new symlinks in the uninstall.sh and install.sh script and some root
file changes because of the new virtlogd init script.
- the archive format changes from tar.gz to tar.xz

For Changelogs see:

https://libvirt.org/news-2015.html
https://libvirt.org/news.html (2017 and later:
https://libvirt.org/news-2016.html )

Signed-off-by: Jonatan Schlag <jonatan.schlag@ipfire.org>
Signed-off-by: Michael Tremer <michael.tremer@ipfire.org>