Merge an applicable subset of r263234 from HEAD to stable/10:

Update most userspace consumers of capability.h to use capsicum.h instead.

auditdistd is not updated as I will make the change upstream and then do a
vendor import sometime in the next week or two.

Note that a significant fraction does not apply, as FreeBSD 10 doesn't
contain a Capsicumised ping, casperd, libcasper, etc. When these features
are merged, the capsicum.h change will need to be merged with them.

Sponsored by: Google, Inc.

Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

If all ioctls are allowed, cap_ioctls_get(2) will return CAP_IOCTLS_ALL.
Update regression tests.

Add regression tests for the new Capsicum system calls.

Sponsored by: The FreeBSD Foundation