[CM] Snd 9.1

[Bill Schottstaedt]

more work on the virtual mix support

Two new hooks: peak-env-hook, draw-mix-hook

added mouse position args to mix-drag-hook

background-gradient (gtk+cairo only)

sound-mark-info

mix-sync-max

moved equalize-panes to snd-motif.scm

new rt-compiler.scm et al thanks to Kjetil

SIGUSR1 (kill -10) throws Snd back to its top level

in cmn: 
  Michael Edwards added a way to change a staff name (new-staff-name)
  I did half of the :old-style layout bugfix (the staves are laid out correctly, I think)

in clm:
  changes for ACL 8.1

Thanks!: Michael Edwards, Etienne Deleflie, Joshua Parmenter, Kjetil Matheussen

checked: Ruby 1.8.6, sbcl 1.0.5, gtk 2.10.12|2.11.0|1, ACL 8.1, pango 1.17.0|1|2, 
         glib 2.13.2|3