Patch Mecanim mirror issue on 5.4?

Hi, we plan to ship our current game on 5.4.1p2. We don't want to jump to 5.5 because of the unknown impact that will have on our build stability and library functionality. We are experiencing the Mecanim issue described here: http://answers.unity3d.com/questions/1254251/animation-events-firing-all-at-once-in-mirrored-bl.html when using the mirror flag on the animation state. We'd like to have this fixed as a patch on 5.4. Is there any way to fix just this Mecanim bug (or update Mecanim), without updating the whole engine to 5.5? Thanks!