Updates x264 to r1259-dd026f2, bringing with it a bunch of changes you can read about...

Updates x264 to r1259-dd026f2, bringing with it a bunch of changes you can read about on their git log. The most prominent change is macroblock tree rate control (read about it on doom9), which is on by default, and for most content it produces smaller, better quality encodes. Due to a minor, temporary issue with fades in baseline profile encodes, for the moment I'm disabling mbtree when bframes=0, but this can be overridden through explicitly specifying mbtree=1 in the x264 options string.

git-svn-id: svn://localhost/HandBrake/trunk@2823 b64f7644-9d1e-0410-96f1-a4d463321fa5