This is the first patch to move the console code out of Xend and into a

This is the first patch to move the console code out of Xend and into a
separate daemon.  In this patch I've included the daemon and a
front-end.  I've also have the console code removed from Xend locally
but I wanted to clarify a few things first before submitting that.

Here's how it works:

1) Daemon sits on control channel (via xcs) waiting for console messages
2) Buffers all console data received
3) Publishes the location of a tty that can be used for reading in
/console/<domid>/tty
4) Reads a value from the store to determine what the limit of console
data should be (/console/<domid>/limit) to prevent DoS attacks

Using it is quite simple, just run consoled and use the xc_console
program to connect to the console.  It uses syslog for logging.

Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>