mmap: remove verbose

The minimum which I think for now
mmap: divide by configure
nlmsg: introduce mnl_nlmsg_batch_reset_buffer for mmap
mmap: just return NL_MMAP_STATUS_COPY hdr

I was wrong, document says:
a message is ready to be processed but could not be stored in the ring, either
because ``it exceeded the frame size'' or because the originating subsystem does
not support memory mapped I/O
configure: no with but enable
mmap: remove mnl_ring_poll_rxframe