[Cin] libvpx via ffmpeg on high-cpu machines

[Andrea paz]

I tried compiling by decommenting "MAX_AUTO_THREADS 16" in the
"pthread_internal.h" file. My processor has 16 threads (8c/16t).
The compilation stops with error. I tried decommenting the line:

#define MAX_AUTO_THREADS 16

I also tried changing the default (16) to 32. I get errors in both cases.
I put the link to cin5.log:
https://ufile.io/hn1vfdtx

[PS: compiling with only the latest patch for memory leaks works well.]