[CM] Snd 11.6

[Bill Schottstaedt]

Snd 11.6

in s7: *#readers* for your own #... readers
       nan? and infinite?
       #nD(...) multidimensional vector constant syntax
       support for circular and shared structures
       integer-decode-float and binary file IO (binary-io.scm).

play-skipping-silence in extsnd.html

removed snd6.scm.

if --with-gtk, the configure script looks first for gtk 3.0 now 
  (actually 2.90.n, but the libraries and headers use the name 3.0), then 
  falls back on 2.0.

added --without-audio configure switch.

checked: sbcl 1.0.38|39, gtk 2.20.1|21.0|90.0|1, mpc 0.8.2

Thanks!: Fernando Lopez-Lezcano, Kjetil Matheussen