This change introduce mac address templating.

By setting lxc.network.hwaddr to something like fe:xx:xx:xx:xx:xx each
"x" will be replaced by a random value.  If less significant bit of
first byte is "templated", it will be set to 0.

This change introduce also a common randinit() function that could be
used to initialize random generator.

Signed-off-by: gza <lxc@zitta.fr>
Acked-by: Serge Hallyn <serge.hallyn@ubuntu.com>