SDL_image and SDL_mixer releases

The final version of SDL_mixer 1.2.9 and SDL_Image 1.2.8 has been released, with the usual list of bugfixes.
Also, Ember has released version 0.5.7, which includes a lot of new nifty authoring features, such as snap-to movement. Also some effort was put into getting it to run correctly (with all nice shader effects) on ATI cards (gret for me, I have an ATI card). And there are lots of speedups, especially in the terrain handling code.