capsicum: use consistent integer types in header

Using uint64_t would require <stdint.h>, but <linux/types.h> is already
included and __u64 is used, so stick to that.
capsicum: return all rights for non-capability

In cap_rights_get(2), if the target file is a normal file then
return all rights rather than -EINVAL.
capsicum: rename CAP_ALL/NONE to CAP_SET_ALL/NONE

CAP_ALL and CAP_NONE sound like values rather than actions, and
are also more generic names (and so more likely to clash with
other things).

This change introduces a deliberate variance from the FreeBSD 10.x
Capsicum kernel API.