[vsipl++] [patch] Add descriptions for FIR class accessors

[Brooks Moses]

Don McCoy wrote, at 10/27/2009 8:48 AM:
> This patch corrects a minor error in an example listed in the Reference 
> Manual.  It also provides more information on the accessors provided by 
> the Fir<> class.
> 
> Ok to commit?

This looks good as well.

Thanks,
- Brooks