[SDL] SDL_image update & png fix

[Sam Lantinga]

> Ah, i got now the right CVS of SDL_image - you are right,
> all looks perfect!

> Hope you release is soon. And the bad link to this old CVS
> should be removed form your active links, is a bit confusing.

It should already be removed.  If it's not, please send e-mail to
slouken at libsdl.org with the location of the bad link.

Thanks,
	-Sam Lantinga, Software Engineer, Blizzard Entertainment