two small changes:
- intercept FIONBIO and FIOASYNC ioctls on netmap file descriptors.
  libpcap calls them to set non blocking I/O on the file descriptor,
  for netmap this is a no-op because there is no read/write,
  but not intercepting would cause fcntl() to return -1
- rate limit and put under netmap.verbose some messages that occur
  when threads use concurrently the same file descriptor.
enable rfc1323 and rfc1644 by default in picobsd images.
I disabled it some 15 years ago but it is useful to have them on
when doing tcp throughput tests.