cso support

[sundance2]

Thanks for the new sdloader binary @swat ! Much appreciated !

Unfortunately, when trying to test it, I get into an immediate crash.
And I believe it's unrelated to the loader itself.

Rather, while within the ISO loader program, when merely _selecting_ the *.cso file,
it instantly crashes.
I think it doesn't reach the point where it tries to load the image.

Presumably, ISO loader does something when selecting the image, like analyzing the header,
and maybe it doesn't expect a ziso header.

I vaguely remember that it was the pb I used to identify when trying to debug this topic earlier this year.

Do you experience the same issue on your side ?