sys/sys/unistd.h: Fill in some missing ACL defines

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>
lib/libposix1e/Makefile: hack in include path for namespace.h header

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