Fix issue #53 by configuring the stack in `connect` rather than in
`listen`.
Tidyups to 3722f0457a2782814455dcd8f5608c695062d05d and #53 fix

* Add some comments about how the DHCP thread should background
* Do not `choose` between listen/configure, since that could be
  scheduled in any order.  Instead, listen before configure and
  background the listen thread.
bump to 1.1.5
Merge pull request #55 from avsm/yomimono-dhcp-without-listen

Further tidyups to #53 fix
Merge branch 'master' of https://github.com/mirage/mirage-tcpip