New window function

[Rob Sykes]

Hello Octave people,

I recently made a C implementation for the Ultraspherical window function which 
might make a useful addition to Octave's 'signal' package. A snapshot with 
Octave wrapper is here: 
https://dl.dropboxusercontent.com/u/8835547/ultrwin.tar.xz

Also included is a replacement implementation for the Dolph-Chebyshev window 
(as a special case of the Ultraspherical window) as it seems that this is gives 
better results than the current one.  Any interest?


Cheers,
Rob