Use helper virProcessRunInMountNamespace in lxcDomainShutdownFlags and
lxcDomainReboot.  Otherwise, a malicious guest could use symlinks
to force the host to manipulate the wrong file in the host's namespace.

Idea by Dan Berrange, based on an initial report by Reco
<recoverym4n@gmail.com> at
http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=732394Signed-off-by: NEric Blake <eblake@redhat.com>
(cherry picked from commit aebbcdd3)

The source code base needs to be adapted as well. Some files
include virutil.h just for the string related functions (here,
the include is substituted to match the new file), some include
virutil.h without any need (here, the include is removed), and
some require both.

introduced by dcf97846

To trigger this cppi needs to be installed.

introduced by dcf97846

When MAXHOSTNAMELEN is set we have to take it's value into account.
Otherwise the build fails on kFreeBSD (FreeBSD kernel and GNU userland)

* Autotools changes:
  - Don't assume Qemu is Linux-only
  - Check Linux headers only on Linux
  - Disable firewalld on FreeBSD
* Initctl:
  Initctl seem to present only on Linux, so stub it on other platforms
* Raw I/O: Linux-only as well
* Headers cleanup

To be able todo controlled shutdown/reboot of containers an
API to talk to init via /dev/initctl is required. Fortunately
this is quite straightforward to implement, and is supported
by both sysvinit and systemd. Upstart support for /dev/initctl
is unclear.
Signed-off-by: NDaniel P. Berrange <berrange@redhat.com>