build a static cockroach binary

edit: latest update at the bottom.


* added a `make build_static`
* vendored in everything that was left: bz2, zlib, protobuf
* build only static libs
* light brushing up of the Dockerfile

next up: a small Cockroach deploy image, built after successful tests through CircleCI.
This is run by the deploy image entry point, meaning that if you mount the tests in the right place they will be executed within the container.
If you run ./mkimage.sh, it will do just that after building, so the script will only give you a zero exit code if the tests pass, validating the image you've just built, at least on this machine.