Versions bump and Changelog update.

In order to start landing ESR 78 related patches without breaking our
nightly builds (which are still ESR 68-based) we hardcode a known good
commit for now.

This update fixes Python 3.8+ compatibility.

These updates include network performance and reliability improvements.

We improve the script in the following ways:

1) Properly check the signature of the MAR files
2) Take #20254 into account
3) Fix all issues `shellcheck` found

We also clean projects/release/dmg2mar since TMPDIR is now set by rbm.

Versions bump and Changelog update.

Versions bump and Changelog update.

`0.9.7.9+deb7u8` is not available anymore for `apt`. Take
`0.9.7.9+deb7u9` from now on.

David Fifield authored Feb 10, 2020 and Georg Koppen committed May 13, 2020

This brings in changes related to
 #33745 Merge a turbotunnel branch
 #33897 Remove buffering from WebRTCPeer
 #34042 Reduce DataChannelTimeout

The new dependencies kcp-go and smux form the new inner session layer.
There's a patch to kcp-go to remove dependencies required for features
we don't use.