capsicum: fill in some CAP_TODO entries

Specifically:

 - For tee(2), the in/out FDs need CAP_READ / CAP_WRITE
   respectively

 - For splice(2), the in/out FDs need CAP_READ|CAP_SEEK or
   CAP_WRITE|CAP_SEEK respectively. (This allows for the
   upcoming change to the semantics of CAP_SEEK, because
   arbitrary file offsets are allowed.)

 - For open_by_handle_at(2), need CAP_LOOKUP right.

 - For Plan9 resource sharing, need CAP_READ|CAP_POLL_EVENT on
   the read FD and CAP_WRITE|CAP_POLL_EVENT on the write FD.

 - For the internally-generated autofs FD need CAP_FSTAT because
   the corresponding inode is accessed (but this check should
   never fire because there is no mechanism for this FD to become
   a capability).

 - For the pipe FD used in autofs need CAP_FSYNC (because the FD
   is changed to be O_DIRECT) and CAP_READ|CAP_WRITE.

 - No specific rights needed to link a second PCM audio FD with
   another.

 - DMA shared buffers need CAP_MMAP|CAP_READ|CAP_WRITE.

 - Multiple-device configuration bitmap file needs CAP_READ.
capsicum: add required rights for timerfd operations

 - For timerfd_gettime, need CAP_READ.
 - For timerfd_settime, need CAP_WRITE and also CAP_READ if the
   old_value argument is non-NULL.
 - Still need CAP_POLL_EVENT to get notification of timer pops
   via poll(2).
capsicum: add required rights for signalfd operations

 - For signalfd/signalfd4 modification of an existing signal FD,
   need new right CAP_FSIGNAL
 - For read(2) need CAP_READ as usual.
 - For poll(2) need CAP_POLL_EVENT as usual.
capsicum: add rights for epoll, eventfd, inotify, fanotify

Specifically:

 - Retrieval of the struct file or struct eventfd_ctx associated
   with an event FD requires CAP_READ|CAP_WRITE|CAP_POLL_EVENT.

 - Modification of an epoll FD's events/FDs requires new right
   CAP_EPOLL_CTL; calling epoll_[p]wait required CAP_POLL_EVENT.

 - Modification of an {fa,i}notify FD's monitored contents requires
   new right CAP_NOTIFY.