GH-74: adb: transport-usb etc. support

Well, I feel like a dick; after implementing this stuff myself I
remembered this issue, and that @xurubin had already come up with a fix
for it: c92eb0dda00c6c499eabb47bd5ce8ef7a273cfa8.

I'm going to go with building on my previous commit, as it enables the
adb-shell-style commands I was originally going for.