gitbuild + emu-vnc

I know, this mixes different things.

Anyway:
1. `emu-vnc` is a simple script to run qemu with vnc; it is very easy to test new builds this way, without downloading them at all
1. `gitbuild.sh` is a script that gets a reference to a commit and builds it. At the moment it is a bit raw in that the main repositories are hardcoded. But it is a pretty base to work on.