linuxmodule ToDevice

https://github.com/kohler/click/pull/75

I changed elements/linuxmodule/todevice.cc back to using ndo_start_xmit
instead of dev_queue_xmit.

I haven't actually tried this out on many different kernel versions, but
I'm curious if any of you have feedback on this set of changes.  I hope to
be able to run this on a few different kernel versions and actually do a
benchmark on my 10Gbps card sometime soon.

Cliff