package/skeleton-init-openrc: new package

package/skeleton-init-openrc: new package

This basic skeleton is similar to skeleton-init-sysv.
All links in /var are same as in skeleton-init-sysv to be compatible
with current default filesystem scheme.

Exceptions:

* /dev/shm and /dev/pts dirs were removed, since they are created by
  openrc devfs service
* /etc/fstab does not need /dev/shm, /dev/pts and /sys entries
  becuse they are mounted by devfs and sysfs services respectively

Signed-off-by: Michał Łyszczek <michal.lyszczek@bofc.pl>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>