access_vectors

Kernel commit 8e4ff6f228e4722cac74db716e308d1da33d744f
(selinux: distinguish non-init user namespace capability checks)
introduced support for distinguishing capability
checks against a target associated with the init user namespace
versus capability checks against a target associated with a non-init
user namespace by defining and using separate security classes for the
latter.  This support is needed on Linux to support e.g. Chrome usage of
user namespaces for the Chrome sandbox without needing to allow Chrome to
also exercise capabilities on targets in the init user namespace.

Define the new security classes and access vectors for the Android policy.
Refactor the original capability and capability2 access vector definitions
as common declarations to allow reuse by the new cap_userns and cap2_userns
classes.

This change does not allow use of the new classes by any domain; that
is deferred to future changes as needed if/when Android enables user
namespaces and the Android version of Chrome starts using them.

The kernel support went upstream in Linux 4.7.

Based on the corresponding refpolicy patch by Chris PeBenito, but
reworked for the Android policy.

Test: policy builds

Change-Id: I71103d39e93ee0e8c24816fca762944d047c2235
Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>