Re: cast ptr ptr to Nim array

[mashingan]

This worked in [my example 
here](https://github.com/mashingan/nimffmpeg/blob/master/fplay.nim#L44)
    
    
    var streams = cast[ptr UncheckedArray[ptr 
AVStream]](pFormatContext[].streams)
    
    Run

I had issues with that too but I fixed my [FFMpeg 
binding](https://github.com/mashingan/nimffmpeg) too.

I even also had some success with [snippet example 
below](https://github.com/mashingan/nimffmpeg/blob/master/ftut.nim#L64)
    
    
    var stream = pFormatContext[].streams[i]
    
    Run