selinux: support wildcard network interface names

Add support for wildcard matching of network interface names.  This is
useful for auto-generated interfaces, for example podman creates network
interfaces for containers with the naming scheme podman0, podman1,
podman2, ...

To maintain backward compatibility guard this feature with a new policy
capability 'netif_wildcard'.

Netifcon definitions are compared against in the order given by the
policy, so userspace tools should sort them in a reasonable order.

Signed-off-by: Christian Göttsche <cgzones@googlemail.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>