[CM] snd 6.10

[Bill Schottstaedt]

Snd 6.10:

bess1.scm and bess1.rb (and many other improvements) 
  thanks to Michael Scholz.

removed read-listener-line from extensions.scm (it's now in
   extsnd.html).
debug.scm with snd-break, snd-trace, snd-debug.
ws-debug and friends for with-sound.
mark-drag-triangle-hook at the suggestion of Matti Airas.
save-mark-properties in marks.scm.
added initial-length arg to new-sound.
added mus_samples_to_seconds and mus_seconds_to_samples to clm.c.

much work on various aspects of mixing:
   renamed mix-position-changed-hook to mix-dragged-hook -- the old
     name was causing endless confusion.  Other names in mix.scm also
     changed (see snd6.scm for backwards compatibility).
   moved mix-sound to mix.scm.
   mix-amp-env-changed-hook.
   changed mix-amp-changed-hook to take 2nd chan arg.
   with-minmax-button in snd-motif.scm.
   drag-and-drop finally works.
   more buttons in the Mix Panel.
   moved mix-name and mix-name->id to snd6.scm.
   next|previous-mix-in-track in mix.scm.
   mus-mix works with CLM output gens (*output*).
   with-mix in ws.scm.

checked: glib/gtk 2.2.2

with much help from: Pat Pagano, Matti Airas, Michael Scholz, 
  Ludger Brummer, Oded Ben-Tal