[CM] LADSPA implementation

[Bill Schottstaedt]

> However, the content of the insound is in there with it ... 

This must be deliberate on the part of the plugin.  Snd doesn't add
anywhere -- it sets the input buffer values from the reader, then
calls the plugin, then writes whatever the plugin returns, again without
adding anything.  I don't know which ambisonics plugin you're
using (or perhaps they're all the same one under 1000 names),
but the "AMB" plugins appear to me to be adding the input back
into the output (I just glanced at the code, and have never paid
much attention to this stuff, so maybe I'm confused) -- ask the
plugin developer what is going on.