[MPlayer-DOCS] [PATCH] ChangeLog updates before release

[Jeff Clagg]

I think there are some additional decoding speed improvements that are
worth mentioning, for instance h.264 decoding is about 20-25% faster on
x86. Would someone mind verifying if the improvement is similar on other
popular architectures?

Additionally, there have been quite a few enhancements to libavcodec's
encoding. Michael Niedermayer and Corey Hickey spent quite some time
looking over tweaks to ratecontrol, scene change detection, and b-frame
placement. Perhaps Corey could render his opinion on whether or not
these changes belong in the ChangeLog?