EMI: Animation priority, blending and fixes

This patch set implements some missing functionality and fixes several issues related to animation.

I discovered a priority field in the .animb animation format that was previously ignored. When multiple animations are played simultaneously, animations with higher priority override animations with lower priority. d55422f adds support for the prioritization. This makes commit 863b33e8 unnecessary, so it is reverted. Animation blending is also implemented, so transitions between animations are now smooth.

See my blog posts http://akzgsoc.blogspot.fi/2014/05/the-summer-of-code-is-finally-here-and.html and http://akzgsoc.blogspot.fi/2014/05/animation-blending.html for more info about animation prioritization and blending.

This patch set fixes at least the issues #872 and #879, but also numerous unlisted ones. For example, the catapult in gme works perfectly now :)

The PR affects many parts of the code and I haven't done a full playthrough yet, so regressions are possible.