Update to olsrd 0.6.7

The Broadband-Hamnet project has moved up to olsrd 0.6.7 in their 3.0.0 release, so I've done the same in hsmm-pi.  (It doesn't seem to be necessary for compatibility, but hsmm-pi may as well pick up the latest fixes and improvements.)

Also I've tested with the latest Raspbian (2014-09-09) and hsmm-pi works fine with it.