Vagrant: update Vagrantfile, fix make testall

Compile libuv from source and use LLVM 3.3. Also, point the testall target at the executable in usr/bin instead of the symlink, which won't exist in the Vagrant build.

Running this through a pull request due to the Make.inc change.

I think I was supposed to have this fixed a couple of weeks ago, so getting it taken care of finally.