[x265] Issue #543: x265 segfault in x265_weight_sp_avx2.loopW / x265::Predict::addWeightUni (multicoreware/x265)

[kucharskim]

New issue 543: x265 segfault in x265_weight_sp_avx2.loopW / x265::Predict::addWeightUni
https://bitbucket.org/multicoreware/x265/issues/543/x265-segfault-in-x265_weight_sp_avx2loopw

Mikolaj:

```
I'm getting segmentation fault in x265 binary or in ffmpeg when
utilizing libx265, every time I run it. Steps to repro are as follows:

1. Download some input file, for example I'm using Big Buck Bunny
wget http://commondatastorage.googleapis.com/gtv-videos-bucket/sample/BigBuckBunny.mp4

2. Use x265 binary:
ffmpeg -i BigBuckBunny.mp4 -loglevel warning -sn -an -f yuv4mpegpipe -pix_fmt yuv420p \
- | \  x265 --y4m --preset veryslow --output movie.265 --input -

3. Alternatively use ffmpeg binary:
ffmpeg -y -i BigBuckBunny.mp4 -sn -an -c:v libx265 -crf 10 -preset veryslow movie.mkv

Both commands end up with SIGSEGV in few seconds.
```

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