[rtmpdump] Unrecognized option

[Howard Chu]

Anders Hasselqvist wrote:
> Hi Howard,
>
> Occasionally I have to resume a download that has failed.
> In those cases I just append "--resume" to the command line.
> On several occasions I have been a bit fast and only typed "-resume"
> or misspelled it in some other way.

That's why I only use single-character options, personally. GNU-style long 
options are vile. They take too long to type, just a waste of space and time.

> Instead of getting an error stating I provided an unknown option, my
> file is just overwritten.
>
> I think that from a user perspective it would be better that rtmpdump
> (and friends) abort when an unknown option is provided.

OK, committed.