Echo sound card driver

Hello,

The fine folks at Echo have finally released their open source driver 
library.  They used the MIT license with one extra non-endorsement 
clause.  I'm not a lawyer but it looked plenty compatible to me so I 
checked the sources in: current/src/add-ons/kernel/drivers/audio/echo/
generic

I also started work on two drivers based on these sources: one for the 
"echo gals" family of cards, and another for the "echo 24" family of 
cards.  I have myself an echo darla (one of the echo gals) so working 
on this is a natural for me.  I invite anyone else who is interested to 
contribute, although maybe waiting a little while may be in order. (I 
just got started 5 hours ago.)

I also checked a nice pdf that explains how to use the library.  Since 
it seemed like documentation I put it in: current/docs/develop/media

Nothing building yet, I'm too tired to work on it atm. :-)  BTW, thanks 
to marcus for the ich driver which I've already started cannibalizing. 
:-)

Andrew