X11: Attempt to disable screen blanking on my HTPC

I say attempt because xorg is a fickle beast, who knows if these options
will actually stop the screen from turning off. I certainly don't!
systemd: No need to stop MPD for XBMC

Since XBMC will be using a PA sink now it will be able to automatically
detect that it can support pass through without having to take exclusive
control of the device.