[CM] Snd 18.6

[bil at ccrma.Stanford.EDU]

Snd 18.6.

clm: Kjetil added a method to the granulate generator to set the jitter 
amount.

s7: changed make-shared-vector to make-subvector (Matlab terminology)
     added subvector?, subvector-position, subvector-vector
     added make-weak-hash-table, weak-hash-table?
     s7 is now thread-safe, I think.
     symbol-setter has been folded into setter.
     c-pointer-info|type|weak1|weak2 (the latter are "weak" values)
     reactive.scm (the old stuff.scm code rewritten).

checked: sbcl 1.4.10

Thanks!: Kjetil Matheussen