[Cin] AOM 3.8, again

[Andrea paz]

>> Any objections to checking libaom v3.8.0 into GIT for wide usage?  Andrew, what about TERMUX?
One possible reason not to upgrade liabaom to 3.8 is that it gets you
even more work. The performance advantage over version 3.4 is there
(in my tests it is a good advantage, in Terje's there is not much
difference), but these become insignificant compared to using svt.
With this the advantage is huge. So one could neglect libaom and keep
only av1-svt.