[PATCH v5 3/4] ubi-utils: ubidump: introduce ubidump

[hujianyang]

> 
> And "-i" / "--info" are not the best names, I think. "-u" / "--ubifs"
> would be better.
> 

Oh, I'd like to reserve this "--ubifs" when we are ready to dump ubi-level
stuff. So in my previous design, "--ubifs" and "--ubi" are used to indicate
only dump the specific area of an eraseblock.

How about an option like "--node" ? Do you insist on "--ubifs" or have
another suggestion?

> And regarding the -l option. What if I do not specify it? What will be
> dumped? Everything? Nothing? I'd vote for duping everything (all LEBs).
> 

It will return an error now, like:

"lnum was not specified (use -h for help)"

Dumping everything is useful and easy to achieve. I will do that~!