New upstream versions of sdl-mixer, sdl-net and sdl-image

[Manuel A. Fernandez Montecelo]

Hello,

I've been working on the new upstream versions and I think that they
are ready, but please review.

In the case of Dominique (or other Debian Devels), please upload -- I
am only DebMaintainer and cannot upload revisions needing new .orig.
files.

Cheers.