FS# 10375: Adds lookahead/attack buffer for DSP functions

[Jeff Goode]

Hi all,

I've been working on this one for a couple of weeks and it's finally 
ready for a first look.  This patch adds a transparent lookahead, or 
attack, buffer to the DSP functions.  It provides the capability of a 
DSP process to look ahead to future samples before processing current ones.

Please take a look and provide feedback.

Thanks!
Jeff