lib/libc/include/{un-}namespace.h: Add ACL functions

Signed-off-by: Edward O'Callaghan <eocallaghan@alterapraxis.com>
sys/kern/syscalls.master: Update with ACL syscalls

Signed-off-by: Edward O'Callaghan <eocallaghan@alterapraxis.com>
sys/sys/vnode.h: Add missing prototype for ACL

Signed-off-by: Edward O'Callaghan <eocallaghan@alterapraxis.com>
sys/kern: misc acl bits

Signed-off-by: Edward O'Callaghan <eocallaghan@alterapraxis.com>
sys/sys/acl.h: resync with FreeBSD

Bring in FreeBSD's version as-is. N.B. Need to forward-port useful
changes on top!

Signed-off-by: Edward O'Callaghan <eocallaghan@alterapraxis.com>
share/man/man9/acl.9

Signed-off-by: Edward O'Callaghan <eocallaghan@alterapraxis.com>
bin/{setfacl,getfacl}: Bring in userland tools for ACL manipulation

Signed-off-by: Edward O'Callaghan <eocallaghan@alterapraxis.com>