[slim-vim] ECL Socket callbacks?

[Brad Beveridge]

Man I'm dumb,  I even responded to your initial posting of that code
with "I don't understand the add-input-listener line", and you told me
what it did!!  Sorry about that.
It shouldn't take me long to rip my current use of standard ECL
sockets out and use the vim network socket instead, yay!  With
handling async Swank data working, I think we will get close to
actually being useful.  Of course, that means writing a manual :)

Brad