Upgrade SDL from 1.2 to 2.0

[tomangelo]

I've chose 0.1.6, because all next milestones include refactoring of some code, and 0.1.6 doesn't, it have only graphic issues, so I thought that this release could have some bigger code change too. Especially if this would make it easier to make new features in a future.
@Raptor: As far as I know, the graphic is mostly written in OpenGL itself, SDL1.2 hasn't so good hardware acceleration, so upgrading this library shouldn't cause any bigger trouble with old hardware. But still I could be wrong, if someone know why this could make any trouble, then he would inform us.