new Delta Update support

[Allan McRae]

On 8/5/22 09:10, Ruben Kelevra wrote:
> Hey guys,
> 
> previously pacman have had a delta update functionality which was (to my
> understanding) removed because of safety concerns and poor performance.
> 
> Since the old delta version was written (and removed) zstd got the ability
> to create delta patches.
>

Thanks.  However I have little interest tying delta support to a 
specific compression algorithm.

Allan