[RFC] Need for a new KIO slave error: "unsupported file format"

[Nicolas Goutte]

I would need a "unsupported file format" for a KIO slave.

As far as I know ERR_UNSUPPORTED_PROTOCOL is the nearest one but probably not 
near enough. (A user might not understand what is meant by protocol in this 
case.)

So probably a new value should be added to kdelibs/kio/kio/global.*. My 
question is how should it be labeled to avoid to have an error message that 
has a too narrow use. 

I propose ERR_UNSUPORTED_FILE_FORMAT with 
"Unsupported file format.\n%1"

The reason I need it is for kdebase/kioslave/tar/tar.cpp . It is needed when 
the archive cannot be opened because the header is somehow not supported/
recognized and I need it also for bug #106908 to at least return the error 
that the compression type of the ZIP is unsupported.

Have a nice day!