[RFC/PATCH] Ubi-Utils: add compare feature

[Alexander Schmidt]

Hi Frank,

> > +#define COMPARE_BUFFER_SIZE 1024
> 
> I think using the something like 2KiB or even the 128KiB would be nicer.

I've played around with several buffer sizes (1KiB, 2KiB, 4KiB and
128KiB), and to my surprise, there was no performance impact.
I've used a 11MiB pfi file and the comparison always takes 5.5 seconds.
But I will change the value to 2KiB, it at least looks nicer.
 
> > +
> >  static const char copyright [] __unused =
> >         "Copyright (c) International Business Machines Corp., 2006";
> 2007

Done.

Thanks for taking a look.
Alex