[CM] Snd 19.8

[bil at ccrma.Stanford.EDU]

Snd 19.8

In Snd, Tito fixed many Snd bugs, involving left-sample and 
right-sample,
   off-by-1 cases for mark-sample and selection-samples, etc.

checked: sbcl 1.5.7

Thanks!: Kjetil Matheussen, David O'Toole, Tito Latini