[arm-allstar] Local monitor speaker for the RPi2

[Steve Zingman]

Since I put up the information to add chan_alsaradio to be used as a 
local speaker for the RPI2
I have been asked if there is a simpler way to achieve a local monitor 
speaker.
After thinking about it for a while I came up with the following:

Do we really need to add alsa just for a speaker?
Do we need to add a channel driver from a outside source?
What else can we do?

We are already using oss for audio on Asterisk. Asterisk has a stock 
channel driver called chan_oss.
It can be used as a simple way to listen to the node on a external speaker.
This does not require much other then a way to adjust the speaker level.

I've posted the basics on git.
<https://github.com/N4IRS/AllStar/tree/master/platforms/rpi/rpi2/monitor>

Thanks to everyone that is feeding back comments. The best way I know of 
to improve things.

73, Steve N4IRS