console: allow VCs to be overridden by UI

We want to expose VCs using a VteTerminal widget.  We need access to provide our
own CharDriverState in order to do this.

Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
Message-id: 1361367806-4599-3-git-send-email-aliguori@us.ibm.com
